FR2463946A1 - Simultaneous prodn. of identical and complementary masks - using resin overlays sensitive to short wave radiation and useful in microelectronics - Google Patents

Abstract

Simultaneous production is described of several high definition identical and complementary masks by exposure to short wave radiation or particle beams esp. for microelectronic applications. The method utilises resins having characteristics which may be positive or negative or may change their characteristics dependant on the applied radiation dose, pref. polymethyl methacrylate, being used. Two uniformly thick substrate layers overlay an absorbant metalic layer each having an overlying radiation sensitive resin. The resin layers may have the same or opposite characteristics, the layer pairs being spaced by 0.1mm. The radiation is parallel or quasi- parallel and perpendicular to the treated surface and is transmitted via the master mask. This is followed by selective removal of the irradiated resins leaving the metal layers as daughter masks.

Description

 The present invention relates to the simultaneous production by a single exposure operation using radiation or particle jets of several identical or complementary high definition masks.

 The surfaces of the masks in question have respectively low and high absorption parts for the radiation which will be used in their application, which most often results in parts having a lack of material and others which have excess . Subsequently, for the sake of language, with regard to these mask parts, we will speak respectively of voids and full. By identical masks we mean masks for which, when superimposed, the full and voids of one coincide with great accuracy respectively with the full and voids of the other over the entire surface of the masks. The masks are said to be complementary when, on the contrary, by superposition, the voids and the full ones are exchanged. Sometimes, with regard to these masks, we will say thereafter, identical masks, that they are of the same polarity and, complementary masks, that they are of opposite polarities.

 Most of the time, the masks are produced by insolation using visible or ultraviolet light radiation of a layer of photosensitive resin, deposited on a substrate possibly surmounted by an underlying absorbent layer, for example metallic, to through a pattern comprising the design of the mask, known as the father mask, the fraction of sunshine energy arriving locally on the resin being a function of the local absorption of the pattern encountered by said energy. Then, a selective dissolution of the parts is carried out irradiated resins (positive resin) or non-irradiated (negative resin) then, by depositing an absorbent layer, for example metallic, on the substrate, or attacking the underlying absorbent layer through the windows thus formed, the locally absorbent layer for the wavelengths of the radiation of future use of the masks, in accordance with the drawing of the parent mask. it goes without saying that in this technique the quality of the duplicate or son mask closely depends on the quality of the pattern inscribed in the resin.

 The production of high resolution masks, especially for microelectronics, is a generally long, complicated, delicate, costly and not very reproducible operation, hence the advantage of manufacturing several at the same time during the course of a single process. Manufacturing. In this connection, the German patent n ° 1 546 592, without going so far as to duplicate masks, describes a process according to which a semiconductor wafer is coated with identical patterns on each of its faces by perpendicular insolation of the wafer using infrared through a mask, the faces of the wafer having been coated with a photosensitive layer of the same resin, of a single polarity. The patterns obtained are from the only category of identical patterns. In addition, the use of long-wavelength infrared radiation leads to poor definition of the edge of the patterns and of the separations between solid and empty, the imprecision being of l 'order of 10 pzm due to the significant diffraction in the infrared range.

 The invention proposes to achieve by a single sun exposure operation, not simple identical patterns on the same support as in the German patent cited, but several separate masks, said masks being of identical or complementary categories and having a much better definition as said grounds. To this end, a first measure taken by the invention is to use, instead of infrared or visible irradiation, irradiation by short wavelength radiation, for example X-ray radiation or else an electron beam. or high energy ions. A second measure taken by the invention relates to the introduction -in the process, of the use of resins of different nature and behavior. They are for example resins whose behavior is either positive or negative, or resins whose behavior reverses from positive to negative when the radiation dose received goes from a low value to a high value. Such a resin is for example polymethylmethacrylate (PEDIA) which is described in the publication "Topics in Applied Physics", vol. 22, pages 53 and 54. In order to obtain a reversal of behavior of several layers of resin of the same kind, one with respect to the other, the invention involves variations in the insolation energy absorbed by each layer , including the parent mask and the substrates along the radiation path.

 According to a first fundamental embodiment of two complementary or identical masks, the method of the invention comprises the following steps: two layers of thick seuruniform substrate, possibly surmounted by an underlying absorbent layer for the wavelengths of the radiation of future use of these masks are each covered with a layer of resin sensitive to short-wavelength radiation (X-ray for example), of positive or negative behavior, different from one layer to another or identical for both; the two substrates provided with their resin layer are placed one above the other and substantially parallel to each other at distances of the order of 10 mm or less, then are subjected to sunshine parallel or almost parallel beam using said radiation perpendicular to their surface through a so-called father mask, the different parts of which are of locally uneven absorption; then we proceed to a selective dissolution of the parts of irradiated resins (positive resin) or not irradiated (negative resin) thus creating identical or complementary patterns, finally by deposition of a metallic absorbent layer on the substrate or attack of the underlying layer absorbent through the windows of these patterns, the locally absorbent layer of each of the complementary or identical masks is formed in accordance with the drawing of the father mask.

 According to a first variant of this embodiment for obtaining identical masks, the two resins are of the same nature or of different natures and each exhibit the same behavior regardless of the radiation dose received.

 According to a second variant, in order to obtain complementary masks, the two resins are of different natures and of opposite behaviors independently of the dose received.

 According to a third variant, also in order to obtain complementary masks, the two layers of resins are of the same nature but the behavior of this same resin is a function of the dose received, the radiation dose sent being adjusted so that the first layer encountered at during the exposure receives a dose causing an inversion of polarity while, for the second layer, the received dose is insufficient to cause this reversal, taking into account the absorbent media traversed by the radiation of exposure.

According to a fourth variant for complementary masks, the two resins are of different natures but of variable behavior as a function of the dose received, the natures and absorptions of the different layers being chosen and the radiation dose sent adjusted to obtain opposite behaviors,
According to a fifth variant for obtaining identical masks, the two resins are of the same nature or of different natures and of variable behaviors as a function of the dose received, the natures and absorptions of the different layers being chosen and the radiation dose sent adjusted by such so that the behavior of the two resins is identical.

 A second embodiment of the invention consists in an extension of this process for the production of several additional masks in number greater than two by means of a single sunstroke. Substrate layers are covered with resins, either of different natures and behaviors, independently of the radiation dose received, or of the same nature, but of different behaviors depending on the dose received, the substrates are placed one above the other. other and substantially parallel at distances of the order of at least 10-1 mm, then the assembly is insulated through a so-called father mask using a dose of radiation such that, taking into account the nature of the resins, the behavior under the action of insolation reverses from one layer to another then after exposure to obtain the masks, the layers of resins and their substrate undergo the same adequate treatments as those indicated for the first mode for carrying out the invention.

 The invention will be better understood using the following description of some embodiments of the invention, which description is accompanied by drawings which represent: - Figure 1: a diagram relating to a variant of a first embodiment of the process of the invention leading to two identical masks.

- Figure 2: a diagram relating to a variant of a first embodiment of the method of the invention leading to two mas
ques complementary.

- Figure 3: a diagram relating to a second embodiment of the
method of the invention leading to a number of masks identi
ques or complementary greater than 2.

In Figures 1 and 2, each relating to a variant
of a first embodiment of the invention, are shown
tees under reference numerals 11 and 12 two layers of substrate
in mylar or polyimide for example. These substrate layers are dis
placed parallel moon above each other. They are each optionally covered with a metallic absorbent layer
not shown for simplification of the drawing and of a layer
resin, respectively 13 and 14, sensitive to radiation
at short wavelength, for example X-radiation.

All the layers are surmounted by the father mask 15
with very different absorption ranges. This mask
is shown schematically by the parts 16, 17, 18, which are highly absorbent for X-rays and the parts 19 and 20 which are weakly absorbent for X-rays.

The set consisting of the mask 15 and the subs layers
trat il et 12 each with their resin is exposed perpendicular
cularily on the plane of the substrates using X-rays diagrammed by the arrows 10.

On layers 13 and 14 only the parts respectively 21, 22,
and 23, 24 are strongly affected by X-ray radiation, with an intensity varying from 21 and 22 to 23 and 24 by a factor equal to the transmission of the substrate 11 and the resin 13.

According to a first variant of this embodiment
corresponding to Figure 1 and for which the masks
are identical, resins 13 and 14 are of the same type
or of different natures, but exhibit the same behavior
for example positive. After exposure the resins are attacked
using a suitable solvent. The parties respectively 21,
22 of layer 13, and 23, 24 of layer 14 are dissolved this
which reveals two identical patterns, the parts of which
thick are 28, 29, 30 and 25, 26, 27 respectively.
then conventionally proceeds to deposit an absorbent layer
metallic, in gold for example, on patterns and substrates or at a
attack of any underlying metallic absorbent layers through the windows provided in the pattern respectively 21, 22 and 23, 24, so as to form two masks with absorbent layer for the wavelength of future use in accordance with the mask design dad. By operating by deposition, identical masks are obtained which are complementary to the father mask, while by operating by attack, said identical masks are identical to the father mask. Let us note in passing that by operating by deposit on one of the substrates and attack on the other, the two masks obtained are complementary.

 According to a second variant of this embodiment corresponding to FIG. 2 and for which the masks produced are complementary, the two resins are of different natures and of opposite behaviors, independently of the dose received, the resin 13 being for example positive and the resin 14 negative.

After exposure to the sun, following an attack with a suitable solvent, the parts respectively 21, 22 of layer 13 and 25, 26, 27 of layer 14 are dissolved, which reveals two complementary patterns the high absorption parts of which are respectively 28, 29, 30 and 23, 24. Two masks complementary to one another are obtained from these patterns by the deposition or attack operations recalled above.

Note also that by operating by deposition on one of the substrates and by attack on the other, the two masks obtained are identical.

 According to a third variant of the embodiment for which the masks produced are complementary, the layers 13 and 14 of FIG. 2 are made of the same resin, the behavior of which reverses from positive to negative when the dose received passes from a low value at a high value. The resin used is, for example, polymethylmothacrylate PAD5A. The 10-sent radiation dose is adjusted so that parts 2, and 22 of layer 13 become negative due to the high dose received, parts 28, 29, 30 being positive, while, on layer 14 , taking into account the absorption in the parent mask 15, the layer 13 and the substrate 11, the dose received corresponds to a positive behavior of the resin in parts 23 and 24 and negative in parts 25, 26 and 27. After dissolution positive parts of layers 13 and 14 have obtained complementary patterns from which have obtained additional masks as recalled above.

 According to a fourth variant of this first embodiment leading to complementary masks, the resins of layers 13 and 14 of FIG. 2 can be of different natures, but of variable behavior with the dose received. The natures and the absorptions of the different layers 13 and 14 and substrates 11, 12 are chosen and the radiation dose 10 in view adjusted to obtain opposite behaviors of the two layers 13 and 14.

 Similarly, a fifth variant of this embodiment leading to identical masks uses for layers 13 and 14 of FIG. 1 resins of the same nature or of different natures and of variable behaviors as a function of the dose received. But then the natures and absorptions of the different layers 13 and 14 and substrates 11, 12 are chosen and the radiation dose 10 sent adjusted to obtain the same behavior for the layers 13 and 14.

 In FIG. 3, relating to a second embodiment of the invention according to which the method is extended to the simultaneous production of a number of masks of variable polarity greater than 2, the layers of substrate, for example polyimide, are represented under the reference numerals 31, 32, 33, 34. These substrates are covered with resin layers, respectively 35, 36, 37, 38. The layers 35 and 36 are for example made of pGlymethylmethacrylate (PMMA) , layer 38 of poly (glycidylmethacrylate-ethylacrylate) (PGMA-EA), with negative behavior and layer 37 of copolymer resin of PIZZA with positive behavior.

All of the substrates and their resin layers are exposed at once using radiation 10 through the parent mask 15. The dose sent from this radiation is adjusted so that layer 35 behaves negatively and the layer 36 positively, taking into account the absorption by substrate 31 and layer 35 and the radiation dose received, layer 37 positively, taking into account the absorptions of substrates 31 and 32 and layers 35 and 36 and layer 38 negatively taking into account the absorptions of the substrates 31, 32 and 33 and of the layers 35, 36 and 37. After exposure, the resin layers are subjected to the action of suitable solvents, making appear, using a single exposure, a series of patterns of variable polarity from one layer to another, identical or complementary / from which a series of identical or complementary masks is deduced by the deposition or attack treatments mentioned above.

Claims (10)

 1. Method for producing on separate supports two complementary or identical high-definition masks using irradiation with short-wavelength radiation, such as for example X-ray radiation or else an electron beam or d ion of high energy, characterized in that it comprises the following stages: two layers of substrate of uniform thickness possibly surmounted by an underlying absorbent metal layer are each covered with a layer of resin sensitive to short radiation wave (X-ray for example), of positive or negative behavior, different from one layer to another or identical for both1 the two substrates provided with their layer are placed substantially parallel one above the other at distances of the order of 10-1 mm or less and then are subjected to a sun exposure in parallel or almost parallel beam using said radiation perpendicular to their surface through a so-called father mask whose different parts have uneven absorption, then selectively dissolve the parts of irradiated (positive resin) or non-irradiated (negative resin) resins thus creating identical or complementary patterns and finally by depositing a metallic absorbent layer on the substrate, or attack of the underlying absorbent layer through the windows of these patterns, the locally absorbent layer of each of the complementary or identical masks is formed in accordance with the design of the parent mask. 2. Method according to claim 1, characterized in that to obtain identical masks, the resins constituting the layers are of the same nature or of different natures and each exhibit the same negative or positive behavior, independently of the dose of radiation received.  3. Method according to claim 1, characterized in that to obtain additional masks the resins constituting the layers are of different natures and opposite behaviors regardless of the radiation dose received. 4. Method according to claim 1, characterized in that in order to obtain additional masks the resins of the layers are of the same nature but the behavior of this same resin depends on the dose received, the dose of radiation devoted to it being adjusted so that the first layer encountered during exposure receives a dose causing an inversion of polarity, while for the second layer, the dose received is insufficient to cause this inversion, taking into account the absorbent media passed through. 5. Method according to claim 4, characterized in that the resin is polymothylmôthacrylate. 6. Method according to claim 1, characterized in that to obtain additional masks, the resins constituting the layers are of different nature and of variable behavior depending on the dose, the natures and absorptions of the different layers of resin and substrate traversed by the radiation during the exposure being chosen and the dose of radiation sent adjusted to obtain opposite behaviors for the two layers of resins. 7. Method according to claim # dication 1, characterized in that, in order to obtain identical masks, the resins constituting the layers are of the same or different nature and of variable behaviors as a function of the dose received, the natures and absorptions of the different layers of resin and substrate traversed by the radiation being chosen and the dose sent adjusted to obtain for the two layers of resin identical behaviors. 8. Extension of the method according to claim t, charac terized in that several layers of substrates, arranged in parallel one above the other, are covered with a layer of photosensitive resins with variable sign behavior from layer to layer. other vis-à-vis the radiation of sunshine from all of the substrates, said quasi-parallel radiation being directed onto the whole from one of its sides and facing a layer of resin through a so-called father mask, of locally uneven absorption then the resin layers after exposure are subjected to the action of a solvent characteristic of the resin and the identical or complementary patterns obtained are subjected to the treatments of deposition of absorbent layer or attack of absorbent underlying layer classirwuespour obtaining from said patterns, identical or complementary masks. 9. Method for obtaining two complementary masks, characterized in that it comprises the same procedure for obtaining identical patterns by irradiation of resin layers and selective dissolution of the irradiated or non-irradiated parts according to one of claims 1, 2 and 7 and in that, then, one proceeds by deposition and attack respectively on one and the other of the identical patterns previously obtained.  10. Method for obtaining two identical masks characterized in that it comprises the same procedure for obtaining additional patterns by irradiating a resin layer and selective dissolution of the irradiated or non-irradiated parts according to one of claims 1, 3 , 4, 5 and 6 and in that, one proceeds by deposit and attack respectively on one and the other of the complementary patterns previously obtained.