Pattern generator for integrated circuits and process of generating patterns by means of said generator

A pattern generator for integrated multilayer circuits, comprising a light source (SLI) for each one of the layers, at least one associated reticle (RETMI) bearing patterns to be reproduced thereon and which is transparent to light, and optical means (MPI) for projecting and focusing the image of the patterns on the layer. The generator is characterized in that with a polarizer (POLI) being connected to the source, the reticle comprises a thin layer (GRI) of magnetooptical material with a magnetization which is at right angles to its surface, the image not the patterns being restituted by a light meter (ANALI).

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a pattern generator, a pattern generating reticle 
and a process for generating patterns utilizing said generator and 
reticle. More particularly, it is applicable to the production of very 
large scale integration (VLSI) circuits used in the electronic circuits of 
information processing systems. 
2. Description of the Prior Art 
The techniques presently used in the production of electronic circuits of 
information processing systems increasingly call for the use of VLSI 
circuits. These integrated circuits are generally offered in the form of 
small rectangular or square wafers, usually called "chips", having sides 
measuring a few millimeters. In current practice, manufacturing 
technologies allow the arrangement of several tens of thousands of 
transistors inside each one of these chips, together with their conductive 
interconnecting networks. 
For the sake of simplicity, an integrated circuit can be defined as a pile 
or stack of different layers on a silicon substrate. These different, 
extremely thin, layers can for example, be composed of silicon oxide, 
phosphosilicate glass, silicon nitrite, polysilicon, metal semiconductors 
or layers of aluminum. During the fabrication of integration circuits, 
several chips that are physically different from one another can be placed 
on the same silicon substrate. Thus, on a silicon substrate having 
dimensions that are essentially the same as those of a disk having a 
diameter on the order of 120 mm, one can produce several tens of chips 
having, for example, the form of squares on one side. When the fabrication 
of all of the chips arranged on a common substrate is complete, they are 
physically separated from one another, e.g., by sawing. 
To prepare each one of the layers of the same chip, the manufacturing 
process thereof consists of several stages which utilize different 
techniques, such as deposition of material on the layer, etching, doping 
of the layer, oxidation of the layer, etc. For each of these different 
stages, it is necessary to delimit on the layer of the chip being prepared 
one or more geographical areas on which is defined a plurality of 
patterns. This operation is carried out by means of a technique usually 
called photolithography. 
Photolithography consists, first, in coating the layer of the integrated 
circuit to be treated with a photosensitive resin. This resin coated layer 
is then lighted or illuminated by an appropriate luminous radiation, 
either through a mask or through a reticle bearing the representation of 
the group of patterns to be reproduced on the area of the layer of the 
integrated circuit to be treated. This latter operation is presently known 
as the name "exposure" operation. 
During this exposure, the illuminated areas of the resin undergo a chemical 
transformation. There are two types of photosensitive resins, namely, 
positive resins and negative resins. In the case of positive resins, one 
exposes (illuminates by luminous radiation) the areas which shall be 
treated by deposition, etchings, paroxidation, etc. In the case of 
negative resins, the areas which shall be protected are covered. 
Regardless of the type of resin, the resin of the exposed areas is 
dissolved in an appropriate chemical bath. Thus, it is obvious that the 
parts of the material coated with resin and which have not been exposed 
remain protected by the resin. One can then proceed to the various 
physicochemical treatments mentioned above using this resin mask. 
As described hereinabove, the resin is illuminated through a mask or 
through a reticle. The mask is a representation on a scale 1 of the areas 
of the resin sought to be protected. During the exposure, the mask is 
brought into direct contact with the resin coated layer of the integrated 
circuit. 
The reticle is a representation on a scale much larger than 1 (usually 
equal to 10) of the patterns that shall be reproduced on the area or areas 
of the resin coated layer to be treated. The image of this reticle is then 
projected in reduced form (the reduction ratio is equal to the reverse of 
the above mentioned ratio, i.e. one-tenth in the case where this scale is 
equal to 10) onto the resin coated layer. 
Thus, at least one reticle or one masking corresponds to a given layer of a 
chip (very large scale integration circuit). 
In view of the foregoing, it is clear that patterns can be generated on 
layers for integrated circuits include a source transmitting a beam of 
light (having a wavelength bordering on near-ultraviolet, for example); 
for each one of the layers, at least one associated reticle bearing 
patterns which shall be reproduced thereon, said reticle being transparent 
to the light beam transmitted by the source; and optical means for 
projecting the image of the patterns onto the layer of integrated circuit 
coated with photosensitive resin. 
The assembly of means defined above is called a pattern generator for 
integrated circuits. 
The chip-bearing substrate is arranged on a table which is insensitive to 
vibrations and is provided with a system enabling the substrate to move in 
accordance with two degrees of freedom, i.e., according to vertical OX and 
OY axes. This table is provided with an extremely accurate positioning 
system and is, for example, equipped with a laser interferometer (for 
example, of the type manufactured by HEWLETT KARD under No. 5501 A and 
described in their technical bulletins). The pattern generator is placed 
on a machine provided with an extremely fine optical alignment system 
which enables it, by means of special sighting marks, to obtain 
positioning accuracies of the chip on which one desires to reproduce the 
patterns in relation to the generator on the order of two-tenths of a 
micron. 
Generally speaking, in current practice, a reticle is produced in the 
following manner: There is produced on a glass substrate (which must be 
transparent to the light beam transmitted by the source) a chromium layer 
which is then coated with an electrosensitive resin. The definition of an 
electrosensitive resin is quite similar to that of a photosensitive resin, 
the only difference being that it undergoes a chemical transformation 
under the action of an electron beam and no longer under the action of 
light. 
If the resin is positive, the patterns are written by an electron beam in 
such a way that the areas which shall be treated (those forming the 
patterns) are exposed to said beam, whereas, if the resin is negative, the 
areas sought to be protected are exposed to the electron beam. The 
electrosensitive resin is then developed in an appropriate chemical bath, 
the chromium is then corroded, in the portions that are no longer 
protected by the resin. 
When the reticle is completed, it is necessary to control the patterns that 
have been written thereon. If for any reason there is an excess of 
chromium on a given location, this excess is evaporated by a laser beam. 
On the other hand, if a pattern of chromium is missing on a given 
location, the whole procedure leading to the writing of the patterns by 
the electron beam as described earlier must be taken up again on said 
location. Experience has shown that if the writing of a reticle with the 
aid of an electron beam is rapid (half an hour), the control thereof is 
very long and may take several days, which makes this latter stage 
extremely expensive. 
The system of stages leading to the generation of patterns on a layer for 
very large integration circuits described above constitutes a process for 
generating patterns on a layer for integrated circuits, whose essential 
successive operations are listed on the table in Appendix I. 
Therefore, a great drawback in pattern generators used in the past as well 
as the generating process utilizing such generators is the mode of 
obtaining the reticle. 
According to the invention, this disadvantage is overcome by replacing the 
reticle formed by a chromium deposit on a glass substrate with a 
magnetooptical reticle having magnetooptical materials and the Faraday 
effect are recalled to mind in the following section. 
Among the magnetic materials having magnetooptical properties one includes 
especially the iron garnets, yttrium and rare earths (gadolinium, terbium, 
etc.). These materials and their magnetooptical properties are, for 
example, described in a paper entitled "Large Stable Magnetic Domains" 
written by G. R. Pulliam, W. E. Ross, B. McNeal, and R. S. Bailey 
published in Applied Physics 53(3), March 1982, pp. 27 54 to 27 58. Said 
materials are transparent to light. For any garnet of this type and, more 
generally, for any magnetooptical material, the magnetooptical effect is 
based on the principle of interaction between a polarized rectilinear 
light and the magnetic state of the garnet or of the material. If this 
interaction takes place because of the transmission of the light through 
the material, the magnetooptical effect is called "Faraday effect". If it 
takes place through reflection, the effect is called "Kerr effect". 
Hereinafter, this description will be limited to the Faraday effect. 
It will be recalled that a light is polarized rectinearly in the plane when 
the electric field vector (and, hence, the magnetic induction vector) 
always retains the same direction in the plane perpendicular to the 
direction of propagation of the radiation. The plane of polarization is 
defined as the plane containing the direction of propagation of the light 
and the electric field vector. 
The result of this interaction is a rotation of the electric field vector 
in the plane perpendicular to the direction of propagation (i.e., in the 
plane of polarization). 
To observe this magnetooptical effect, a polarized rectilinear (preferably 
monochromatic) beam of light is transmitted over the surface of the 
magnetooptical garnet whose magnetization is usually normal to said 
surface (the garnet is said to have a vertical magnetization). It is 
observed that after passing through the layer of magnetic garnet, the 
electric field vector of the polarized light undergoes a rotation in the 
plane of polarization which, by convention, is considered equal to an 
angle (-.theta.) when the light encounters an area of the garnet where the 
magnetization is called negative (i.e., having the same direction of 
propagation of light and being equal to (+.theta.) as the polarized light 
passes through a zone where the magnetization is positive (direction 
opposite to the direction of propagation of the light). 
To write patterns on the magnetooptical reticle, it suffices simply to 
write thereon by means of a magnetic or thermomagnetic transducer of the 
type used currently in magnetic disk storages domains of magnetization 
(e.g., positive) having the form of the patterns sought to be reproduced 
on a given layer for a very large scale integration circuit, the remainder 
of the reticle surface (except patterns) having a negative magnetization. 
A magnetic transducer is usually composed of a magnetic circuit around 
which a winding is arranged and which includes an air gap. 
A thermomagnetic transducer is formed, on the one hand, by a point-shaped 
heat source which allows the temperature of the magnetic material to rise 
locally above its Curie point or its point of compensation and, on the 
other hand, by a system which creates a permanent magnetic field having an 
intensity which is sufficient to orient the magnetization of the 
previously heated part during its cooling. 
To project the image of the patterns (formed by the magnetic domains with a 
positive magnetization) of the reticle onto the resin coated layer for 
very large scale integration circuits, the reticle is illuminated with a 
polarized light beam. As it passes through the domains with a positive 
magnetization (the patterns), the electric field vector of the light 
undergoes a rotation equal to (+.theta.), whereas, as it passes through 
the areas of the reticle external to the domain forming the patterns, the 
electric field vector of the polarized light undergoes a rotation in the 
plane of polarization which 9 is equal to (-.theta.). If there is placed 
between the reticle and the layer of the integrated circuit a light meter 
formed by a crystal oriented in its direction of propagation and arranged 
in such a way that said direction is at right angles to the direction 
occupied by the electric field vector of the transmitted light as the 
latter passes through a domain with a negative magnetization, a light with 
zero intensity is absorbed at the outlet of the light meter as the light 
passes through a domain with a negative magnetization, whereas a light 
having non-zero intensity is absorbed as the light passes through a domain 
with a positive magnetization (one pattern). 
In other words, due to the presence of the light meter, everything happens 
as if only domains with a positive magnetization transmitted the light. It 
should be obvious that the light meter could be placed differently, so 
that only domains with a negative magnetization transmits the light. 
Thereby, one can project the image of the domains with a positive 
magnetization (patterns) on the layer for integrated circuits onto which 
one seeks to reproduce these patterns. 
SUMMARY OF THE INVENTION 
According to the teachings of the invention, the pattern generator for 
integrated circuits composed of a pile or stack of different layers, 
comprises: a source transmitting a light beam; for each one of the layers, 
at least one associated reticle bearing patterns to be reproduced thereon 
and which is transparent to the light beam from the source; optical means 
for projecting the image of the patterns onto the layer coated with 
photosensitive resin. 
This generator is characterized by the fact that a light polarizer is 
connected to the source and the reticle comprises a thin layer of 
magnetooptical material with a magnetization which is perpendicular to its 
surface, where the patterns are formed by magnetic domains with a given 
shape and having a magnetization which is opposite to the magnetic 
environment surrounding them, the image of the patterns being reinstituted 
by a light meter. 
The invention also relates to a process of generating patterns on a layer 
for integrated circuits which comprises the following operations or steps: 
1. formation of a reticle by depositing a thin layer on a medium which is 
transparent to light, and the writing of patterns thereon; 
2. verification of the patterns thus obtained; 
3. coating of the layer for integrated circuits with photosensitive resin; 
4. projection of the image of the reticle onto the layer for integrated 
circuits; and 
5. development of the image of the patterns projected onto the layer in a 
bath which dissolves the parats of the layer exposed to light during the 
projection of the image of the reticle. 
This process is characterized in that: 
(a) the formation of the reticle is obtained by depositing a thin layer of 
magnetooptical material having a magnetization which is at right angles to 
its surface on the medium which is transparent to light; 
(b) the writing of the patterns on the reticle is effected by means of a 
magnetic or thermomagnetic transducer; 
(c) the verification of the patterns is effected by means of a magnetic 
transducer or a transducer using the magnetooptical effect; and 
(d) the restitution of the image is effected by means of an assembly formed 
by a light polarizer and a light meter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For a better understanding of the constructional principles and the 
operation of the pattern generator for integrated circuits according to 
the invention, it is useful to recall to mind the pattern generators as 
known in the prior art and shown in FIGS. 1 and 2 as well as the 
principles of photolithography, shown in FIGS. 3 and 4 and, finally, the 
Faraday effect of magnetooptical garnets shown in FIGS. 5a, 5b, and 5c. 
Now referring to FIG. 1, which shows the main elements of a pattern 
generator GMA as known in the prior art. 
These constituent elements are as follows: 
a light source SLA; 
a RETA reticle; and 
means MPA for projecting the image of the patterns carried by the reticle 
RETA on a layer for integrated circuits such as one of the chips , 
to arranged on a silicon substrate WAFA. 
The silicon substrate WAFA is placed on a table interferometer TABINTA. The 
position of each one of the chips to is marked very accurately by 
a measuring system with an interferometer that uses, for example, a laser 
interferometer of the type 5501A of HEWLETT KARD. The marking of the 
chips is effected in relation to a system of rectangular axes OX, OY. 
The assembly of elements forming, on the one hand, the pattern generator 
and, on the other, the silicon substrate provided with its chips to 
are aligned in relation to each other by an extremely fine optical 
alignment system that uses special sighting marks, the accuracy of 
alignment of the chips in relation to the generator being on the order of 
two-tenths of a micron. 
As can be seen in FIG. 2, the reticle RETA which includes a medium STLA 
which is transparent to light, e.g., a glass substrate, on which a thin 
layer of chromium COCR (the description of the mode of obtaining such a 
reticle is given hereinabove) is deposited. The patterns shown in FIG. 2 
are supposed to have been obtained by corroding or etching the chromium 
layer COCR, so that a beam of light can be transmitted therethrough. 
The operation of the pattern generator GMA is known in the prior art. To 
this end, the light source LA transmits a parallel beam of light FLA. The 
light is transmitted by the patterns of the reticle RETA. The projection 
means MPA project the reduced image of the patterns onto one of the chips 
arranged on the substrate WAFA. As can be seen in FIG. 1, the images of 
the patterns of the reticle RETA are projected onto the chip . As a 
rule, the reduction ratio of the patterns of the reticle to their images 
on the chips to is 1:10. The reduced image of the patterns of the 
reticles RETA is projected onto the layer of resin CORESA previously 
deposited on the layer CMCI of the wafer , said layer being, in turn, 
deposited on the silicon substrate WAFA, (cf. FIG. 3). The various stages 
of obtaining, by etching patterns on the layer CMCI of the chip by 
means of a photolithographic process, are shown in FIGS. 4a to 4d. These 
various stages are as follows: 
(a) exposure: The beam of light FLA passes through the patterns of the 
reticle RETA and is transmitted by projection means MPA, which project the 
reduced image thereof onto the resin layer CORESA which coats the layer 
CMCI of the wafer (FIG. 4a). If the resin CORESA is a positive resin, 
the parts thereof which are exposed correspond to the patterns sought to 
be reproduced on the layer and which are those of the reticle RETA. 
(b) development: the resin layer CORESA enters an appropriate chemical bath 
where it is developed. Only the parts that have been exposed (cf. FIG. 4a) 
are dissolved by this chemical bath. The resin layer CORESDEV is obtained 
in this manner. 
(c) etching of the patterns: through the resin mask CORESDEV the layer CMCI 
is etched at the sites which have been mentioned with reference to FIG. 
4a. This results in the etched layer CMCIG. 
(d) dissolution of the resin: The resin is dissolved in a chemical bath. 
One of the layers forming the chip is then produced and one can 
proceed to the next stage of the manufacturing process of the chip. 
Now, reference will be made to FIGS. 5a, 5b and 5c. 
FIG. 5a shows a thin layer (several microns) to several tens of microns 
thick) of a magnetooptical garnet GRMF having a perpendicular 
magnetization, that is to say, where the magnetization is normal to the 
surface layer. A certain number of magnetic domains with small dimensions 
(several microns to several tens of microns) are written on said garnet, 
only three of which are shown in FIGS. 5a for the sake of simplicity. 
These domains are, respectively, Di-1, Di, Di+1. The respective magnetic 
induction vectors of each of said domains are Bi-1, Bi, Bi+1. 
An incident polarized, rectilinear light beam Fi according to a direction 
of propagation DPi is transmitted at right angles to the surface of the 
garnet GRMF. In a propagation plane PPR normal to the direction of 
propagation DPi the electrical field of the incident light polarized, 
rectilinear light beam Fi is Ei and has the direction indicated in FIGS. 
5a, 5b and 5c, FIGS. 5a and 5b being views in the space of the plane PPR, 
while FIG. 5c is a projection onto said plane PPR. A polarization plane of 
the light beam Fi is defined by the direction of propagation DPi and the 
vector Ei and is called PPOLi. 
It is assumed that the magnetooptical garnet GRMF can transmit light. In 
these conditions, as the rectilinear, polarized light beam passes through 
the garnet GRMF it becomes the transmitted beam Ft. As the mean Fi passes 
through a magnetic domain with a negative magnetization, such as the 
domain Di, the transmitted beam is such that its electrical field Et- has 
rotated by an angle (-.theta.) relative to the field Ei of the incident 
beam Fi. The polarization plane of the transmitted beam Ft is then PPOLt-, 
the dihedral angle between said plane and the plane PPOLi also being equal 
to (-.theta.). 
Likewise, as the incident beam Fi passes through a magnetic domain with a 
positive magnetization, such as, e.g., the domain Di+1 (Di-1) of induction 
Bi+1, the transmitted beam Ft is such that its electrical field Et+ 
undergoes a rotation (+.theta.) in relation to the electrical field Ei of 
the incident beam Fi. The polarization plane PPOLt+ then encloses with the 
plane PPOLi a dihedral angle equal to (+.theta.). 
FIG. 5b allows a better view of the relative positions of the electrical 
fields Ei, Et-, Et+ of the beams Fi and Ft, depending on whether Fi 
passses through a magnetic domain with a negative or positive 
magnetization. 
To determine the direction of magnetization of each one of the domains Di, 
which amounts to determining whether the electric field vector has turned 
an angle (-.theta.) or an angle (+.theta.), a light meter element is 
placed on the propagation path of the transmitted beam Ft. The latter is 
usually composed of a crystal having a privileged direction of 
transmission of the polarization of the light, e.g., DPP, said direction 
being indicated by the solid lines in FIG. 5c. The light meter element is 
arranged such that this privileged direction DPP is normal to the 
electrical field Et-. 
At the light meter outlet a light is absorbed whose luminous intensity is 
proportional to the square of the projection of the electric field vector 
onto the privileged direction DPP. Thus, if the beam Ft passes through a 
domain with a negative magnetization, a light will be absorbed at the 
light meter output having a luminous intensity which is proportional to 
the square of the module of the vector Etp-, projection of the vector Et- 
onto the direction of polarization DPP. Likewise, if the beam Ft passes 
through a domain with a positive magnetization (such as Di+1), a light 
will be absorbed at the light meter output having a luminous intensity 
which is proportional to the square of the module of the vector Etp+, 
projection of the vector Et+ onto the direction DDP. 
Thus, it is apparent that if the beam Ft has passed through a domain with a 
negative magnetization, a light will be absorbed at the light meter output 
which is almost zero, whereas, if the beam Ft has passed through a domain 
with a positive magnetization, a light will be absorbed at the light meter 
output having a luminous intensity which is not zero. 
As stated above, the main drawback of the prior art pattern generators is 
the fact that the mode of producing and controlling the reticle is long 
and expensive. The present invention enables these disadvantages to be 
overcome by replacing the reticle of the prior art pattern generator by a 
magnetooptical reticle formed by the deposit of a thin magnetooptical 
layer with the Faraday effect onto a substrate which is transparent to 
light, e.g., a layer of magnetooptical garnet whose properties are those 
mentioned hereinabove and illustrated in FIGS. 5a, 5b and 5c. 
As apparent from FIGS. 6 and 7, the pattern generator of integrated 
circuits according to the invention (GMOI) comprises the following 
elements: a light source SLI; a polarizer POLI; a magnetooptical reticle 
RETMI; a light meter ANALI: projecting means MPI; means MPI for projecting 
the image of the patterns of the reticle RETMI onto a chip PAI placed on a 
silicon substrate WAFI. The latter is, in turn, placed on an 
interferometer table TABINTI of the same type as the interferometer table 
TABINTA shown in FIG. 1. The silicon substrate WAFI has n chips , , 
. . . , PAi, . . . PAn. 
The assembly of elements of the pattern generator according to the 
invention GMOI on the one hand and the interferometer table TABINTI1 on 
the other hand are mounted in such a way that they are insensitive to 
vibrations. 
The assembly of elements constituting the pattern generator GMOI, on the 
one hand, and the chip PAi, on the other, must be aligned with a high 
degree of precision in relation to each other. This alignment is effected 
by means of an extremely fine optical alignment system, allowing an 
accuracy of alignment on the order of two-tenths of a micron. 
As apparent from in FIG. 8, the reticle RETMI has a magnetooptical garnet 
having a thickness of from a few microns to several tens of a micron 
deposited on a substrate which is transparent to the light STLI. The 
magnetooptical garnet GRI has a magnetization which is at right angles to 
its surface. FIG. 8 shows several patterns MOT1, MOT2, MOT3, written on 
the magnetooptical garnet sought to be reproduced on the chip PAi. It 
stands to reason that the latter has been previously coated with a 
photosensitive resin layer CORESI. 
The properties required for the magnetooptical garnet GRI of the reticle 
RETMI are as follows: 
(a) have a strong rotation through the Faraday effect (angle called 
-.theta. or +.theta. in FIG. 5) in order to have at the output of the 
light meter ANALI a strong light contrast between the transmitted light 
corresponding to a domain with a negative magnetization and the 
transmitted light corresponding to a domain with a positive magnetization. 
The magnetic materials utilized to produce these garnets can have a 
Faraday effect to bring about a rotation higher than 50.000 degrees/cm 
which produces at the output of the light meter a light contrast of 250 
for a garnet one micron thick. This means that if the light transmitted by 
a domain with a negative magnetization has a luminous intensity 
coefficient of 1, the light transmitted by a domain with a positive 
magnetization has a coefficient of 250; 
(b) a weak absorption of the light, which allows one to avoid the heating 
of the material and the use of too powerful light sources; 
(c) the possibility of producing these garnets on large surfaces on the 
order of 100.times.100 mm; and 
(d) a very small density of defects. 
FIGS. 9 and 10 show in greater detail the three patterns MOT1, MOT2 and 
MOT3 of the magnetooptical garnet GRI shown in FIG. 8. These three 
patterns are formed by magnetic domains D1, D2, D3 having the particular 
shapes indicated on these same FIGS. 9 and 10. The magnetization in each 
one of the domains D1, D2, D3 is oriented upward and is thus supposed to 
be positive, whereas all the surface of the garnet GRI which does not 
constitute the domains (i.e., without the domains D1, D2, D3) has a 
magnetic domain which is oriented downward and, therefore, considered to 
be negative. 
The operation of the pattern generator according to the invention GMOI is 
as follows: The light source SLI sends a parallel light beam FLI which, as 
it passes through the polarizer POLI, is polarized by the latter and 
becomes the polarized beam of light FLPI. This beam passes through the 
magnetooptical garnet and undergoes a rotation of its polarization plane 
through the Faraday effect equal to (-.theta.) if, for example, magnetic 
domains are involved with a negative magnetization (i.e., the surface of 
the garnet GRI which does not belong to the magnetic domains forming the 
patterns) and undergoes a rotation (+.theta.) as it passes through the 
domains where the magnetization is positive, i.e., the domains D1, D2, D3 
which form the patterns sought to be reproduced on the chip PAi. 
The light meter ANALI is supposed to be so arranged that at its output the 
light which has passed through the domains with a negative magnetization 
has an almost zero intensity, while the light transmitted by the domains 
with a positive magnetization has an intensity which is not zero (the 
ratio between the intensities due to the traversing of the domains with, 
respectively, a negative and a positive magnetization is, for example, on 
the order of 250, as stated earlier). Thus, one can say that the light 
meter ANALI restitutes the image of the patterns D1, D2, D3. 
The projecting means MPI project a reduced image (usually on a scale 1:10) 
of the patterns of the reticle RETMI onto the resin layer CORESI. Thus, 
the resin CORESI is exposed according to the images of the patterns MOT1, 
MOT2, MOT3, and is then developed. One can then perform on the thin layer 
for integrated circuits CMCII of the chip PAi the successive operations 
which have been described in FIGS. 4c and 4d. 
Now, referring to FIG. 11 which shows one embodiment of a device for 
writing patterns DEMI designed to write the patterns on a magnetooptical 
garnet such as GRI. 
This device DEMI comprises: 
a writing magnetic transducer TMEVI; and 
a transducer medium TMEVI opposite which an interferometer table TABINTI2 
can move on which the magnetooptical garnet GRI is placed. 
Preferably, the magnetic transducer TMEVI is a magnetic transducer of the 
integrated type similar to that described and claimed in patent 
application No. 80.07453 filed Apr. 2, 1980 by Compagnie Internationale 
Pour L'Informatique Cii-Honeywell Bull entitled "Magnetic Transducer With 
An Air Gap Of Large Variable Dimension For Reading and Writing Data 
Contained On A Magnetic Medium" and corresponding to U.S. Pat. Ser. No. 
242,924, now U.S. Pat. No. 4,386,383, filed Mar. 12, 1981. This transducer 
TMEVI comprises a first polar piece PP1 and a second polar piece PP2 
between which there is arranged a winding BOBI. The polar pieces PP1 and 
PP2 are designed in the form of piles of thin successive magnetic and 
insulating layers, while the winding BOBI is constructed in the form of a 
pile of thin successive conductive and insulating layers. Both polar 
pieces PP1 and PP2 are magnetically coupled to the end which is farthest 
away from the magnetooptical garnet GRI and are placed at the other end 
which is closest to said magnetooptical garnet substantially 
perpendicularly thereto so as to form the air gap there. The transducer 
has two thin layers of air gap CMME1 and CMME2 whose magnetic properties 
are such that, depending on the strength of the current flowing through 
the winding BOBI, the air gap has a large dimension varying between a 
minimum value GDMIN and a maximum value GDMAX. 
Preferably, the polar pieces PP1 and PP2 are made from anisotropic material 
having a direction of easy magnetization DFA and a direction of difficult 
magnetization DDA. 
To write domains representing the patterns which shall be reproduced on the 
chip PAi, such as the domains D1, D2, D3 shown in FIGS. 8, 9, 10, a 
current with a positive strength, for example, is made to flow through the 
winding BOBI and proper to the width of the lines of the patterns sought 
to be traced on the layer CMCII. These patterns are recorded in the form 
of domains with a positive magnetization. 
In contrast, if one wishes to impart a negative magnetization, (i.e., apart 
from the patterns sought to be reproduced), a current with a negative 
strength is made to flow through the winding BOBI of the transducer TMEVI. 
It is obvious that once the domains D1 to D3 are written on the garnet GRI, 
it is extremely simple to verify whether they have been written properly, 
i.e., whether they have been written at the desired locations, with the 
desired dimensions. This verification can be effected by means of an 
appropriate magnetic or magnetooptical transducer. 
Thus, one sees immediately the advantage of the magnetooptical reticle used 
in the pattern generators taught by the invention; a relatively simple 
design and extremely (hence, inexpensive) pattern-writing and verifying 
operations which can be carried out with a magnetic or thermomagnetic 
transducer of the current type for the writing and with a magnetic or 
magnetooptical transducer of the current type for the verification. 
From the foregoing one can easily deduce the sequence of operations 
constituting the process of generating patterns using the pattern 
generator according to the invention. These various operations are 
summarized in the table of Appendix II (after the desription). By 
comparing this table in Appendix II with that in Appendix I, one will be 
able to ascertain the greater simplicity of the pattern-generating process 
using the pattern generator of the invention compared with the process of 
generating patterns as known in the prior art. 
PROCESS OF GENERATING PATTERNS ON A LAYER FOR INTEGRATED CIRCUITS AS KNOWN 
IN THE PRIOR ART 
APPENDIX I 
FIRST OPERATION 
Manufacture of a reticle: 
(a) depositing a thin layer on a medium which is transparent to light 
(e.g., this layer is made from chromium); 
(b) depositing an electrosensitive resin on the chromium layer; 
(c) writing patterns on the reticle by means of an electron beam; 
(d) developing the resin in an appropriate chemical bath; 
(e) corrosion of the chromium on the sites where the resin has been 
dissolved in the chemical bath. 
SECOND OPERATION 
Verification of the patterns obtained: 
(a) if a line is missing, it is necessary to resume the process of 
generating patterns according to the first operation by depositing a new 
layer of chromium; 
(b) if there is one line too much, it is made to disappear by illuminating 
it with a high-energy laser beam; 
(c) when the reticle is correct, one proceeds to the third operation. 
THIRD OPERATION 
Coating of the integrated circuit layer of photosensitive resin. 
FOURTH OPERATION 
Projection of the image of the reticle onto the layer for integrated 
circuit coated with resin. 
FIFTH OPERATION 
Developing the image of the patterns projected onto resin protecting the 
layer of the integrated circuit by dissolution of the parts of the resin 
exposed to lighting the fourth operation. 
PROCESS OF GENERATING PATTERNS ON A LAYER FOR INTEGRATED CIRCUIT ACCORDING 
TO THE INVENTION 
APPENDIX II 
FIRST OPERATION 
Manufacture of the magnetooptical reticle by depositing a layer of 
magnetooptical garnet on a medium which is transparent to light and 
writing of the patterns on the reticle by means of a magnetic or 
thermomagnetic writing transducer. 
SECOND OPERATION 
Verification of the patterns of the reticle by means of a magnetic 
transducer or by utilizing the magnetooptical effect. If a line is missing 
it is easy to rewrite it by means of the writing transducer mentioned 
above. If there is one line too much, it is erased by means of the same 
writing transducer (by sending to the winding thereof a current which 
flows in a direction opposite to that with which the excess line was 
written). 
THIRD OPERATION 
Identical to the third operation in the table of Appendix I. 
FOURTH OPERATION 
The restitution and projection of the image of the reticle onto the layer 
for integrated circuits are effected by means of an assembly comprising a 
polarized light source, a light meter, and projecting means. 
FIFTH OPERATION 
Similar to the fifth operation in the table of Appendix I.