CA1204527A - Polymeric films for electronic circuits - Google Patents
Polymeric films for electronic circuitsInfo
- Publication number
- CA1204527A CA1204527A CA000432475A CA432475A CA1204527A CA 1204527 A CA1204527 A CA 1204527A CA 000432475 A CA000432475 A CA 000432475A CA 432475 A CA432475 A CA 432475A CA 1204527 A CA1204527 A CA 1204527A
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- CA
- Canada
- Prior art keywords
- films
- film
- electronic circuits
- circuit
- plasma
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02107—Forming insulating materials on a substrate
- H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
- H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
- H01L21/02123—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon
- H01L21/02126—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02107—Forming insulating materials on a substrate
- H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
- H01L21/02205—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates the layer being characterised by the precursor material for deposition
- H01L21/02208—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates the layer being characterised by the precursor material for deposition the precursor containing a compound comprising Si
- H01L21/02214—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates the layer being characterised by the precursor material for deposition the precursor containing a compound comprising Si the compound comprising silicon and oxygen
- H01L21/02216—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates the layer being characterised by the precursor material for deposition the precursor containing a compound comprising Si the compound comprising silicon and oxygen the compound being a molecule comprising at least one silicon-oxygen bond and the compound having hydrogen or an organic group attached to the silicon or oxygen, e.g. a siloxane
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02107—Forming insulating materials on a substrate
- H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
- H01L21/0226—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process
- H01L21/02263—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process deposition from the gas or vapour phase
- H01L21/02271—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process deposition from the gas or vapour phase deposition by decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition
- H01L21/02274—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process deposition from the gas or vapour phase deposition by decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition in the presence of a plasma [PECVD]
Abstract
ABSTRACT
POLYMERIC FILMS FOR ELECTRONIC CIRCUITS
Electronic circuits are described in which plasma-deposited polysiloxane films 45 are used as protective and dielectric layers. Such layers are highly advantageous in that, they are chemically inert, exhibit excellent thermal stability and have low dielectric constant. Electronic circuits with these films may be processed at relatively high temperatures without damage and have minimum parasitic capacitances where conductor spacing is extremely small and access times are very short. The layers are particularly useful for high density, high frequency memory and logic circuit.
POLYMERIC FILMS FOR ELECTRONIC CIRCUITS
Electronic circuits are described in which plasma-deposited polysiloxane films 45 are used as protective and dielectric layers. Such layers are highly advantageous in that, they are chemically inert, exhibit excellent thermal stability and have low dielectric constant. Electronic circuits with these films may be processed at relatively high temperatures without damage and have minimum parasitic capacitances where conductor spacing is extremely small and access times are very short. The layers are particularly useful for high density, high frequency memory and logic circuit.
Description
5~
T,F. IlE'rAJC~YK 2 the invention involves electronic circuitB wi th polymeric films used as insulator and dielectric layers.
The ever continuing advance in VLSI technology have led to greater packing density and shrinking design rules. Thi3 has created a need for new and improved dielectric materials or use in various device ~t~ctures.
or example, the close proximity of various conducting elements in the VLSI circuit has created a need for dielectric material Or low dielectric cons tant so a to reduce parasitic capacities. Also required it high dielectric strength beeause of toe close approach oY
various conducting elements in the VLSI circuits. The uge o-f two or lore levels of metalliza~ion creates the necd for dielectric material with other unique properties. For example, it i9 desirable in some cases that the diclectric be applied at relatively low temperature so as to not adversely affect tile multilevel o circuit, In other cases, processing of these multilevel circuits often involves the use ox relatively high temperatures to which the dielectric material ~u~t be stableO ~Iso, the reduced feature sizes and higher applied voltages ~`ound in new VLSI devices may require Jew 25 materials for glassiIication and encap~u:LationO
llesira~le propert,ies for dielectric layerq ln use for Vl-SI circuits are low dielectric constants Jo a to 28 minimize l)arasitic capacitances, high thermal stability so as to permit furtller processing of the circuit at high tempera-tures, relatlvely low application temperature so as to minimize damage -to the circuit on appli¢ation o:e the dielectrict high dielectrie ~tren~th, Good adherence Good film intagrity (i.e., freedom from craolcs) and chemical stability par-ticularly to water and water vapor.
Such a dielectric material wowld be extremely valuable and particularly for applicatloll to high derl~.lty circuits because reduced parasitic capacitances would permit higher peed and thermal stability would permit greater flexibllity in processing 9UCtl circuit, A number of studies have been jade of the use ox polymer films in ele¢tronic circuit both a an insulator and as an encapsulating filln and a pas~ivat-l~g film.
Most noteworthy of thee are as follows: A. Szeto end D.W. Hess in a paper entitled "Correlation of Chemical and Electrical Properties of Plasma - Deposited Tetramethylsilane Films", I 903 (1981), have studied tlle properties of tetrame~hylsil~ne films of interest in electric cir¢ult ~brication. Similar studies have been carried out for polymer film made by plasma induced polymerization of hexamethyldl~iloxane. these studies have been reported in the hollowing papers: US. Maisonneuve et al, Thin Sol ia pp. 209~2:L6 (1977); M. Akti~ et al 9 (9), pp. 5055-5057 (1~80)~
M, Mai00nneuve et l Thin ' PP- 35-~1 (1976), and J.~. ~leluber~-Sapieha, ACC i d k (1), pp~ 1~4-105 (1980 3 .
According to the present invelltio~ thare it provlded a semiconductor eleotrical apparatus comprising semiconductor ma-teri~l and conducting elelltants 9 characterizcd in that the apparatus ~7lrther oo~pri~
polysiloxarle ~iltn made by plasma-induced polymeriza~-lon 35 ox at least one al~ylalkoxysilalle with thy alkyl and alkoxy group contairling up to 3 oarbon atums~
A preferred embodiment ox the invent:Lon provide 38 a electri.eal circui t i5~ witch at least part ox a ~llrface of the circuit is covered with a plasma-deposited polysiloxane film in which the monomer is an alkylalkoxysilane The alkyl and alkoxy groups s~lould jot contain more -than three carl)on atoms. Typiaal examples are trimethylmethoxysilane, dlmettlyldimethoxysilane, triethylet~loxysilane, e-tc. YrereIred is the monomer trimethylmet~loxysilane because Or low dielectric constant high breakdown voltage, low film stresses and a reasonable degree of thermal stability and high hydrophobicity. The polymer film is useful for a large variety of electrical circuits, high frequency, low frequency, direct current, etc. Typically, a circuit comprises a substrate conductor elemcnts, input connec-tions, output conIlections~ etc. These films are hlghly advantageous where at least Rome ox the conductor spacings are very low (i.e., of` the order of 2 microns or less) and circuit frequenci~3s (or corresponding access times) are very high (i.e., greater than 5 I
It is also highly advantageous where aluminum metallization is use-l or other metallization where thermal cycling ls required.
For a better unders-tanding of the invention reference is made to the accompanying drawings in which FIG, 1 show a graph of same data on dielectric constant for polysilo~a}le films maze from a variety of alkylalkoxysilane~;
IG. 2 shows a graph ol` same data on breakdown voltage for polysilo~ane films made from a variety of alkylalkoxysilanes;
3~ FIG. 3 shows a graph of same data on thermal effect on film thickIiess for pvlysilo~ane film made from a variety of alkylal~oxysilanes;
FIG. shows a ¢ross-sectional view OI a portion of a -typical integfated circuit showing cer-tain Ieatures 3~ of such oircuit intluding a cap layer jade of a ~olysiloxan~ material;
~I~7 5 ghow~ a cross-sec-tic)nal view of a portion 38 a more cvmplex i ntegrated circuit with a cap material ~¢p~s~
made in accordance Wittl an embodimetlt of the inventlon;
and FIG. 6 shows cro~s-sectional view of a portion ox an integrated circuit in which polysiloxarle ls used as an in-terlevel dielectrlc to separate two level o-f aluminum metallization.
It has been ~iscoYered, tha-t certain silicon-containing polymer made by plasma-polymerization Y
certain oxygen-cont~ining organosilicon compounds yield polysiloxane polymer films wi-th unusually good properties or use in integrated circul-ts, especially VLSI-type cir¢uits with high densities of circuit elements and short access times (-typically less tllan lO 6 o-r 10-7 seconds). The films can be ol` benefi-t to a large variety of circuits. Such clrcuits preferably contain semiconductor materîal (e.g. 7 silicon, germaniut~3 galliula arsenide, etc.), substra-te (O:~tOtl also the semiconducting material), conductor elements (e.g., alumirlum) and various doped region.
Yarious alkylalkoxysila}les may be used as monomers proYided the number old carbons in the alkyl group and the number ox carbons in the alkoxy group does no exceed thrse. Generally uy to 20 percen-t of substances outside this class may be used to alter the properties ox the polymer (filler, cro~s~linking agents, property mow iers ox various kinds, etc.). Although or most applica~,ions, tie monomer should mainly consist of the class describe above. More than one alkylalkoxysilane may be used as the monomer although ordinarily only a single monolller is u3sd. Preferred are alkylalkoxy~ila-le monomers in whicll the alkyl group are methyl grour,s. Most preferred is the trimethylmethoxysilane monomer because the resulting polymer has Yery low dielec-tric constant, high thermal stability and excellent adherence properties These pro~-erties are highly advalltageous or many circuit applications or a number of reasons, Dielectric 3~ col~stant often limits access tiines and clock ~re~uencies LS~7 in many memory and logic circuits. Therlllal cycling is often required in tlle abri.cation Oe integrated circuits, especially t,i~ose con1;<linillg aluminum COndUCtirl~ elemelltS. AllllerellCe i8 e~p~cially important in ellc~l)sulution applLcat,ion~ arld wtlere multil):le conducting 1ayers are used.
Thy thickness of Layors Illay vary over large limits (often as thin as 0.05 fin and usually del)en~s on the par-ticu1ar applicatioll. Typica1 is from 0.2 to 10 100 micrumeters. For many circtlit appl1cations, thicknesses from 0.5 to ].0 mi(:rolne-ters usually yield satisfactory resul-tY. For dally ap~licatiollsg the sho-u1d be as thin as possib1e without :incurring any deleterious effects. For ex~tmple, in some circuit 15 applications, it is deslrab1t~ -to minimLze -thickness so as to minimize capacitallce e~feots ill mailltain suffioient thickness to prevent Yo1tage breakdown and di~usion through the film. O~tesl opt1mum thickness prom this poin-t of v:iew occurs be-tween 0.5 and 2 20 nlicrometers.
A plasma discharge procedure is used to produce the polymer film ~roln the mollomer. Satis:eactory result are obtained prom conventional procedures described in cletail in a number of ~)oolss alld referellces. Typical books 25 are edited by J.R, ~lollaban alld A.'r. Bell (Wiley-Interscience, New York 1974), espec:ial.ly M. M.i1Lard, Chnl)ter 5, page 177 and , edited by My Shen and A.T. Bell, ACS Symposium Series No. 108 (~nerican 30 l,he~ical Society9 Washington, D,C., 1979).
The parti¢u1aI appaIa-tus used ill the experiments described below i5 typical of e(iuipment used for plasma-induced polymer:iza-tionO The li:Lms were deposited in a parallel plate, lo cm d:iameter, radial slow reactor. The 35 electrode zap was tout 2 cm and the operat:Lng frequency about 13~56 Mi~z. ~otll the OF' excited electrode and the rounded (suscep-tor) plates were water cooler at a temperatllre oi' about 35~ le~rees C.
4S~7 The reagents were obtained commercially and uere used without further preparation. All the chemicals used were liquids at room temperature and flow rates were adjusted using a needle valve to give a system pressure of 50 millitorr in the absence of a plasma. The pressure without the introduction of monomer was about 5 millitorr. The plasma was operated at about 50 volts and films were deposited on a precleaned silicon substrate mounted on the bottom grounded plate, Film thickness and refractive index were determined ellipsometrically with an Ellipsometer II* (Applied Materials Corp), with film thicknesses cross-checked using a Nanospec* (Nanometrics). Film stoichiometry was determined from Rutherford backscattering measurements.
Film stress measurements were obtained using an optically-levered laser beam method wherein stress is determined from changes induced in the radius of curvature of a substrate after a fi]m is deposited; Contact angle measurements were made using a Rame-Hart* goniometer.
Electrical properties were obtained by first evaporating Al dots on the films and, in the case of the dielectric constant determination, obtaining a C-V curve and measuring the capacitance in accumulation; Breakdown voltage measurements were obtained by probing lO0 dots per film and measuring the voltage required to pass 2~ A of current;
Various monomers were used in these experiments, corresponding to 0/Si mole ratios from zero (tetramethylsilane) or l (trimethylmethoxysilane) to (tetramethoxysilane); the experiments showed that deposition rate is essentially the same (about 60 Angstroms per minute) for 0/Si ratios from one to four.
Film stress is essentially zero for 0/Si ratios of zero and increases from about 3 to 5xlO8 dynes per square centimeter as 0/Si ratios increase from one to four. Such stresses are quite reasonable for most applications ~Z!~?45~7 - 6a -including use in circuit applications, The polysiloxane polymers become less *Trade Mark l '" `~ ^
5~7 hydrophobic as the ratio 0/Si increases from one to rOur with both tetramethylsilane and tri~ethylmethoxy silsne most hydrophobic, Index of refraction decreases modestly with increasing ratio of 0/Si from 0 -to I, Of paIticular slgni~icance is the dielectric behavior of the film as a function ox film compositioll, FIG, 1 shows a graph of dielectric constant versus fllm composition (in terms of monomer starting material), As stated aboYe, low dielectric constant is highly 10 advantageous in modern circuit applications, Dielectric constant it a minimum for 0/Si ratio ox one (corresponding to the monomer trimethylmetho~ysilane). Largely because of this low dielectric constant and other Good properties ox this polymer, the polymer resulting -from plasma-15 induced polymerization of trimethylmethoxysilane is~o~t prsferred, The dielectric strength of the films were also measured. The dielectric strength was quite low for 0/5i equal to 0 and 4. The average values were less than 20 100 volt per micrometer, However, or 0/Si ratio 1 and 3.(trimethylmethoxysilalle and methyltrimethoxysilane, respectively), the breakdown voltage averaged in excess of several hundred volts per mierometer.
A convenient way of evaluating the breakdown 25 charaoteristics of a film is to plot the "sport population against monomer composition. The "sport"
population it -the percent of dot probed that have breakdown voltages less than lOQ volts per micrometer.
Suoh data are shown in FIG. 2 for various starting 3o monomers. q'he particularly low values or 0/Si ratios ox 1 and 3 are highly advantageous ln applications involving electrical circuits. The other 0/Si ratios may be higher due t,o the softness ox the films and the probe used in the measurements.
The thermal properties of several polysiloxane films were alto examined, This was done by exposlng the film to a temperature of 300 (legrees C for one hour in 38 air and measuring the percent reductioll in film thlckness, ~;~$45~
The results of these experiments are given in FIG. 3.
Here, the percent reduction in thickness i5 pLotted as a function of the ratio of O/Si ox tlle monomer U9e~.
Although all the polymer films exhibit excellent thermal stability, the the~lal s-tability Or the polymer film made from trimethylmethoxysilane :i8 especially good.
The thickness was oily reduced by nbout 2.5 percent aster being exposed to the heat treatment described above Although all ox the polymer films made from alkyl~lkoxysilane mono~lers exhibit excellent properties particularly for electronic applications, the polymer films made from trimethylmethoxysilane exhibit exceptionally good properties or such applica-tions.
The dielectric constant and film stress are minimal or near minimal, wl-ile propertles such as hydrophobicity, dielectric strength and the~nal stability are maximum or near maximum. Aclditional e~)eriments showed that polymer Yilms made by plasma-induced polymerization o-f trimethylmethoxysilane has excellent adhesion as 20 evidenced by the Scotch tape pull test and survlving a patterning process on a topographical surface. The film is readily patterned using a O + 2 plasma but is quite resistant to an 0~ P1LISma. this permits plasma 3tripping of resist in the l3resence of the polysilo~ane 25 film. The thermal stability was particularly impressive as evidenoed by the tact that even a-t 450 degrees C
in the presence of worming gas or nitrogen, the film contracts only a few percent.
FIG lo shows a cross-sectional view of a typical 30 inteerated circuit 1l with various features as labeled (such as pi channels, no channels, etc.). The circuit it convenlently described as a CMOS (Complementary Metal Oxide Semlconductor3 circuit with a single tubt single polysillcon structure cxhibiting jive micrometer de6ign 35 rules. The exact features ox the integrated circuit are not critical to understandillg the invention and will bc descrlbed only briefly. The substrate ox the circuits is 38 made of relatively heavily l doped silicon (typically I)hosphorus dopell in the concentration range of roughly 1018 atoms per cubic centimeter). ibis region is marked n+ in the diagram. A li~hter-doped l'egion covers -the rl~ region (marked n and various other regions are marked such as PTUB regiorls, no channels and p* channe'ls, The UNSTOP region is used to electrically isolQte one region rrom another. An oxide region if is also part of the circuit, This oxide is usually SiO2 and is often called a field oxide or FOX region. A polysilicon region 42 and aluminum region ~t3 are alYo shown as well as glass region 44 (usuLIlly phosphorus glass). The entire circuit is covered with a layer of plasma-poly~eri~ed polysiloxane 45. Usually the thickness varies between 0.5 and 2 mierometers.
FIG. 5 shows a side view of a more complex CMOS
PTUB an rub a well a9 p type channels (PCh) and n-type channels (nCl~) There are also regions of heavy p-type doping (p+~ and heavy n-type doping (no).
Certain reglons have very thin oxide layers 51 usually 20 made of SiO2 and some thicker oxide layers 52 again usually SiO2) often referred -to a yield oxide or FOX.
where is also a layer ox TaSi2 53 (often polycrystalline silicon is used in the same capacity) and various conducting layers 5l~ usually made of aluminum. Layers oi phosp~lorus glass 55 are also used in the structure.
As a capping layer 56, a polysiloxane layer i9 pUt town by plasma~induced polymeri:~ation of trlmethylsnethoxysilane over the entire structure. The film is used as a protcctive layer an is usually about one micrometer 30 thick FIGo 6 shows a somewhat more complex structure 60 wlth many of the l'eatures shown in FIG. 6 including gate oxide 61, i`ield oxide 62~ TaSi2 layer 63, phospho~ls glass layer 64 and aluminum layer 65. Alto shown it the 3'j polysiloxane layer 66 covering a large portion ox the circuit. A particular di~l'erence between this circuit and the circuit shown in FtG. 5 is the use ox a top 38 aluminum metal layer to selectively contact a bo-ttom ~Z~45~7 - 10 .
aluminum metal layer. Ilere, lie ~olysiloxane is use not only as an encapsulating layer but also a an interlevel dieleotrlc to sepa-ate the top level ox aluminum prom the rest of the circu:it.
"
3o
T,F. IlE'rAJC~YK 2 the invention involves electronic circuitB wi th polymeric films used as insulator and dielectric layers.
The ever continuing advance in VLSI technology have led to greater packing density and shrinking design rules. Thi3 has created a need for new and improved dielectric materials or use in various device ~t~ctures.
or example, the close proximity of various conducting elements in the VLSI circuit has created a need for dielectric material Or low dielectric cons tant so a to reduce parasitic capacities. Also required it high dielectric strength beeause of toe close approach oY
various conducting elements in the VLSI circuits. The uge o-f two or lore levels of metalliza~ion creates the necd for dielectric material with other unique properties. For example, it i9 desirable in some cases that the diclectric be applied at relatively low temperature so as to not adversely affect tile multilevel o circuit, In other cases, processing of these multilevel circuits often involves the use ox relatively high temperatures to which the dielectric material ~u~t be stableO ~Iso, the reduced feature sizes and higher applied voltages ~`ound in new VLSI devices may require Jew 25 materials for glassiIication and encap~u:LationO
llesira~le propert,ies for dielectric layerq ln use for Vl-SI circuits are low dielectric constants Jo a to 28 minimize l)arasitic capacitances, high thermal stability so as to permit furtller processing of the circuit at high tempera-tures, relatlvely low application temperature so as to minimize damage -to the circuit on appli¢ation o:e the dielectrict high dielectrie ~tren~th, Good adherence Good film intagrity (i.e., freedom from craolcs) and chemical stability par-ticularly to water and water vapor.
Such a dielectric material wowld be extremely valuable and particularly for applicatloll to high derl~.lty circuits because reduced parasitic capacitances would permit higher peed and thermal stability would permit greater flexibllity in processing 9UCtl circuit, A number of studies have been jade of the use ox polymer films in ele¢tronic circuit both a an insulator and as an encapsulating filln and a pas~ivat-l~g film.
Most noteworthy of thee are as follows: A. Szeto end D.W. Hess in a paper entitled "Correlation of Chemical and Electrical Properties of Plasma - Deposited Tetramethylsilane Films", I 903 (1981), have studied tlle properties of tetrame~hylsil~ne films of interest in electric cir¢ult ~brication. Similar studies have been carried out for polymer film made by plasma induced polymerization of hexamethyldl~iloxane. these studies have been reported in the hollowing papers: US. Maisonneuve et al, Thin Sol ia pp. 209~2:L6 (1977); M. Akti~ et al 9 (9), pp. 5055-5057 (1~80)~
M, Mai00nneuve et l Thin ' PP- 35-~1 (1976), and J.~. ~leluber~-Sapieha, ACC i d k (1), pp~ 1~4-105 (1980 3 .
According to the present invelltio~ thare it provlded a semiconductor eleotrical apparatus comprising semiconductor ma-teri~l and conducting elelltants 9 characterizcd in that the apparatus ~7lrther oo~pri~
polysiloxarle ~iltn made by plasma-induced polymeriza~-lon 35 ox at least one al~ylalkoxysilalle with thy alkyl and alkoxy group contairling up to 3 oarbon atums~
A preferred embodiment ox the invent:Lon provide 38 a electri.eal circui t i5~ witch at least part ox a ~llrface of the circuit is covered with a plasma-deposited polysiloxane film in which the monomer is an alkylalkoxysilane The alkyl and alkoxy groups s~lould jot contain more -than three carl)on atoms. Typiaal examples are trimethylmethoxysilane, dlmettlyldimethoxysilane, triethylet~loxysilane, e-tc. YrereIred is the monomer trimethylmet~loxysilane because Or low dielectric constant high breakdown voltage, low film stresses and a reasonable degree of thermal stability and high hydrophobicity. The polymer film is useful for a large variety of electrical circuits, high frequency, low frequency, direct current, etc. Typically, a circuit comprises a substrate conductor elemcnts, input connec-tions, output conIlections~ etc. These films are hlghly advantageous where at least Rome ox the conductor spacings are very low (i.e., of` the order of 2 microns or less) and circuit frequenci~3s (or corresponding access times) are very high (i.e., greater than 5 I
It is also highly advantageous where aluminum metallization is use-l or other metallization where thermal cycling ls required.
For a better unders-tanding of the invention reference is made to the accompanying drawings in which FIG, 1 show a graph of same data on dielectric constant for polysilo~a}le films maze from a variety of alkylalkoxysilane~;
IG. 2 shows a graph ol` same data on breakdown voltage for polysilo~ane films made from a variety of alkylalkoxysilanes;
3~ FIG. 3 shows a graph of same data on thermal effect on film thickIiess for pvlysilo~ane film made from a variety of alkylal~oxysilanes;
FIG. shows a ¢ross-sectional view OI a portion of a -typical integfated circuit showing cer-tain Ieatures 3~ of such oircuit intluding a cap layer jade of a ~olysiloxan~ material;
~I~7 5 ghow~ a cross-sec-tic)nal view of a portion 38 a more cvmplex i ntegrated circuit with a cap material ~¢p~s~
made in accordance Wittl an embodimetlt of the inventlon;
and FIG. 6 shows cro~s-sectional view of a portion ox an integrated circuit in which polysiloxarle ls used as an in-terlevel dielectrlc to separate two level o-f aluminum metallization.
It has been ~iscoYered, tha-t certain silicon-containing polymer made by plasma-polymerization Y
certain oxygen-cont~ining organosilicon compounds yield polysiloxane polymer films wi-th unusually good properties or use in integrated circul-ts, especially VLSI-type cir¢uits with high densities of circuit elements and short access times (-typically less tllan lO 6 o-r 10-7 seconds). The films can be ol` benefi-t to a large variety of circuits. Such clrcuits preferably contain semiconductor materîal (e.g. 7 silicon, germaniut~3 galliula arsenide, etc.), substra-te (O:~tOtl also the semiconducting material), conductor elements (e.g., alumirlum) and various doped region.
Yarious alkylalkoxysila}les may be used as monomers proYided the number old carbons in the alkyl group and the number ox carbons in the alkoxy group does no exceed thrse. Generally uy to 20 percen-t of substances outside this class may be used to alter the properties ox the polymer (filler, cro~s~linking agents, property mow iers ox various kinds, etc.). Although or most applica~,ions, tie monomer should mainly consist of the class describe above. More than one alkylalkoxysilane may be used as the monomer although ordinarily only a single monolller is u3sd. Preferred are alkylalkoxy~ila-le monomers in whicll the alkyl group are methyl grour,s. Most preferred is the trimethylmethoxysilane monomer because the resulting polymer has Yery low dielec-tric constant, high thermal stability and excellent adherence properties These pro~-erties are highly advalltageous or many circuit applications or a number of reasons, Dielectric 3~ col~stant often limits access tiines and clock ~re~uencies LS~7 in many memory and logic circuits. Therlllal cycling is often required in tlle abri.cation Oe integrated circuits, especially t,i~ose con1;<linillg aluminum COndUCtirl~ elemelltS. AllllerellCe i8 e~p~cially important in ellc~l)sulution applLcat,ion~ arld wtlere multil):le conducting 1ayers are used.
Thy thickness of Layors Illay vary over large limits (often as thin as 0.05 fin and usually del)en~s on the par-ticu1ar applicatioll. Typica1 is from 0.2 to 10 100 micrumeters. For many circtlit appl1cations, thicknesses from 0.5 to ].0 mi(:rolne-ters usually yield satisfactory resul-tY. For dally ap~licatiollsg the sho-u1d be as thin as possib1e without :incurring any deleterious effects. For ex~tmple, in some circuit 15 applications, it is deslrab1t~ -to minimLze -thickness so as to minimize capacitallce e~feots ill mailltain suffioient thickness to prevent Yo1tage breakdown and di~usion through the film. O~tesl opt1mum thickness prom this poin-t of v:iew occurs be-tween 0.5 and 2 20 nlicrometers.
A plasma discharge procedure is used to produce the polymer film ~roln the mollomer. Satis:eactory result are obtained prom conventional procedures described in cletail in a number of ~)oolss alld referellces. Typical books 25 are edited by J.R, ~lollaban alld A.'r. Bell (Wiley-Interscience, New York 1974), espec:ial.ly M. M.i1Lard, Chnl)ter 5, page 177 and , edited by My Shen and A.T. Bell, ACS Symposium Series No. 108 (~nerican 30 l,he~ical Society9 Washington, D,C., 1979).
The parti¢u1aI appaIa-tus used ill the experiments described below i5 typical of e(iuipment used for plasma-induced polymer:iza-tionO The li:Lms were deposited in a parallel plate, lo cm d:iameter, radial slow reactor. The 35 electrode zap was tout 2 cm and the operat:Lng frequency about 13~56 Mi~z. ~otll the OF' excited electrode and the rounded (suscep-tor) plates were water cooler at a temperatllre oi' about 35~ le~rees C.
4S~7 The reagents were obtained commercially and uere used without further preparation. All the chemicals used were liquids at room temperature and flow rates were adjusted using a needle valve to give a system pressure of 50 millitorr in the absence of a plasma. The pressure without the introduction of monomer was about 5 millitorr. The plasma was operated at about 50 volts and films were deposited on a precleaned silicon substrate mounted on the bottom grounded plate, Film thickness and refractive index were determined ellipsometrically with an Ellipsometer II* (Applied Materials Corp), with film thicknesses cross-checked using a Nanospec* (Nanometrics). Film stoichiometry was determined from Rutherford backscattering measurements.
Film stress measurements were obtained using an optically-levered laser beam method wherein stress is determined from changes induced in the radius of curvature of a substrate after a fi]m is deposited; Contact angle measurements were made using a Rame-Hart* goniometer.
Electrical properties were obtained by first evaporating Al dots on the films and, in the case of the dielectric constant determination, obtaining a C-V curve and measuring the capacitance in accumulation; Breakdown voltage measurements were obtained by probing lO0 dots per film and measuring the voltage required to pass 2~ A of current;
Various monomers were used in these experiments, corresponding to 0/Si mole ratios from zero (tetramethylsilane) or l (trimethylmethoxysilane) to (tetramethoxysilane); the experiments showed that deposition rate is essentially the same (about 60 Angstroms per minute) for 0/Si ratios from one to four.
Film stress is essentially zero for 0/Si ratios of zero and increases from about 3 to 5xlO8 dynes per square centimeter as 0/Si ratios increase from one to four. Such stresses are quite reasonable for most applications ~Z!~?45~7 - 6a -including use in circuit applications, The polysiloxane polymers become less *Trade Mark l '" `~ ^
5~7 hydrophobic as the ratio 0/Si increases from one to rOur with both tetramethylsilane and tri~ethylmethoxy silsne most hydrophobic, Index of refraction decreases modestly with increasing ratio of 0/Si from 0 -to I, Of paIticular slgni~icance is the dielectric behavior of the film as a function ox film compositioll, FIG, 1 shows a graph of dielectric constant versus fllm composition (in terms of monomer starting material), As stated aboYe, low dielectric constant is highly 10 advantageous in modern circuit applications, Dielectric constant it a minimum for 0/Si ratio ox one (corresponding to the monomer trimethylmetho~ysilane). Largely because of this low dielectric constant and other Good properties ox this polymer, the polymer resulting -from plasma-15 induced polymerization of trimethylmethoxysilane is~o~t prsferred, The dielectric strength of the films were also measured. The dielectric strength was quite low for 0/5i equal to 0 and 4. The average values were less than 20 100 volt per micrometer, However, or 0/Si ratio 1 and 3.(trimethylmethoxysilalle and methyltrimethoxysilane, respectively), the breakdown voltage averaged in excess of several hundred volts per mierometer.
A convenient way of evaluating the breakdown 25 charaoteristics of a film is to plot the "sport population against monomer composition. The "sport"
population it -the percent of dot probed that have breakdown voltages less than lOQ volts per micrometer.
Suoh data are shown in FIG. 2 for various starting 3o monomers. q'he particularly low values or 0/Si ratios ox 1 and 3 are highly advantageous ln applications involving electrical circuits. The other 0/Si ratios may be higher due t,o the softness ox the films and the probe used in the measurements.
The thermal properties of several polysiloxane films were alto examined, This was done by exposlng the film to a temperature of 300 (legrees C for one hour in 38 air and measuring the percent reductioll in film thlckness, ~;~$45~
The results of these experiments are given in FIG. 3.
Here, the percent reduction in thickness i5 pLotted as a function of the ratio of O/Si ox tlle monomer U9e~.
Although all the polymer films exhibit excellent thermal stability, the the~lal s-tability Or the polymer film made from trimethylmethoxysilane :i8 especially good.
The thickness was oily reduced by nbout 2.5 percent aster being exposed to the heat treatment described above Although all ox the polymer films made from alkyl~lkoxysilane mono~lers exhibit excellent properties particularly for electronic applications, the polymer films made from trimethylmethoxysilane exhibit exceptionally good properties or such applica-tions.
The dielectric constant and film stress are minimal or near minimal, wl-ile propertles such as hydrophobicity, dielectric strength and the~nal stability are maximum or near maximum. Aclditional e~)eriments showed that polymer Yilms made by plasma-induced polymerization o-f trimethylmethoxysilane has excellent adhesion as 20 evidenced by the Scotch tape pull test and survlving a patterning process on a topographical surface. The film is readily patterned using a O + 2 plasma but is quite resistant to an 0~ P1LISma. this permits plasma 3tripping of resist in the l3resence of the polysilo~ane 25 film. The thermal stability was particularly impressive as evidenoed by the tact that even a-t 450 degrees C
in the presence of worming gas or nitrogen, the film contracts only a few percent.
FIG lo shows a cross-sectional view of a typical 30 inteerated circuit 1l with various features as labeled (such as pi channels, no channels, etc.). The circuit it convenlently described as a CMOS (Complementary Metal Oxide Semlconductor3 circuit with a single tubt single polysillcon structure cxhibiting jive micrometer de6ign 35 rules. The exact features ox the integrated circuit are not critical to understandillg the invention and will bc descrlbed only briefly. The substrate ox the circuits is 38 made of relatively heavily l doped silicon (typically I)hosphorus dopell in the concentration range of roughly 1018 atoms per cubic centimeter). ibis region is marked n+ in the diagram. A li~hter-doped l'egion covers -the rl~ region (marked n and various other regions are marked such as PTUB regiorls, no channels and p* channe'ls, The UNSTOP region is used to electrically isolQte one region rrom another. An oxide region if is also part of the circuit, This oxide is usually SiO2 and is often called a field oxide or FOX region. A polysilicon region 42 and aluminum region ~t3 are alYo shown as well as glass region 44 (usuLIlly phosphorus glass). The entire circuit is covered with a layer of plasma-poly~eri~ed polysiloxane 45. Usually the thickness varies between 0.5 and 2 mierometers.
FIG. 5 shows a side view of a more complex CMOS
PTUB an rub a well a9 p type channels (PCh) and n-type channels (nCl~) There are also regions of heavy p-type doping (p+~ and heavy n-type doping (no).
Certain reglons have very thin oxide layers 51 usually 20 made of SiO2 and some thicker oxide layers 52 again usually SiO2) often referred -to a yield oxide or FOX.
where is also a layer ox TaSi2 53 (often polycrystalline silicon is used in the same capacity) and various conducting layers 5l~ usually made of aluminum. Layers oi phosp~lorus glass 55 are also used in the structure.
As a capping layer 56, a polysiloxane layer i9 pUt town by plasma~induced polymeri:~ation of trlmethylsnethoxysilane over the entire structure. The film is used as a protcctive layer an is usually about one micrometer 30 thick FIGo 6 shows a somewhat more complex structure 60 wlth many of the l'eatures shown in FIG. 6 including gate oxide 61, i`ield oxide 62~ TaSi2 layer 63, phospho~ls glass layer 64 and aluminum layer 65. Alto shown it the 3'j polysiloxane layer 66 covering a large portion ox the circuit. A particular di~l'erence between this circuit and the circuit shown in FtG. 5 is the use ox a top 38 aluminum metal layer to selectively contact a bo-ttom ~Z~45~7 - 10 .
aluminum metal layer. Ilere, lie ~olysiloxane is use not only as an encapsulating layer but also a an interlevel dieleotrlc to sepa-ate the top level ox aluminum prom the rest of the circu:it.
"
3o
Claims (13)
1. A semiconductor electrical apparatus comprising semiconductor material and conducting elements, characterized in that the apparatus further comprises polysiloxane film made by plasma-induced polymerization of at least one alkylalkoxysilane with the alkyl and alkoxy groups containing up to 3 carbon atoms.
2. Apparatus according to claim 1, wherein the alkyl group is a methyl group.
3. Apparatus according to claim 2, wherein the alkoxy group is a methoxy group.
4. Apparatus according to claim 3, wherein the alkylalkoxysilane is trimethylmethoxysilane.
5. Apparatus according to claim 1, wherein the conducting elements comprises aluminum.
6. Apparatus according to claim 1, wherein the thickness of the polysiloxane film is between 0.05 and 100 micrometers.
7. Apparatus according to claim 6, wherein the thickness of the polysiloxane film is between 0.5 and 10 micrometers.
8. Apparatus according to claim 7, wherein the thickness of the polysiloxane film is between 0.5 and 2.0 micrometers.
9. Apparatus according to claim 1, wherein at least two of the conducting elements have spacing less than two microns.
10. Apparatus according to claim 1, wherein the semiconducting material is selected from silicon, gallium arsenide and germanium.
11. Apparatus according to claim 10, wherein the semiconducting material is silicon.
12. Apparatus according to claim 11, wherein the semiconducting electrical apparatus is a memory circuit.
13. Apparatus according to claim 11, wherein the semiconducting electrical apparatus is a logic circuit,
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US40800582A | 1982-08-13 | 1982-08-13 | |
| US408,005 | 1982-08-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1204527A true CA1204527A (en) | 1986-05-13 |
Family
ID=23614453
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000432475A Expired CA1204527A (en) | 1982-08-13 | 1983-07-14 | Polymeric films for electronic circuits |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5948929A (en) |
| BE (1) | BE897503A (en) |
| CA (1) | CA1204527A (en) |
| DE (1) | DE3329065A1 (en) |
| FR (1) | FR2531811B1 (en) |
| GB (1) | GB2125423B (en) |
| IT (1) | IT1203708B (en) |
| NL (1) | NL8302845A (en) |
Families Citing this family (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60225447A (en) * | 1984-04-23 | 1985-11-09 | Mitsubishi Electric Corp | Manufacture of semiconductor device |
| EP0204631A3 (en) * | 1985-06-04 | 1987-05-20 | Fairchild Semiconductor Corporation | Semiconductor structures having polysiloxane leveling film |
| US4723978A (en) * | 1985-10-31 | 1988-02-09 | International Business Machines Corporation | Method for a plasma-treated polysiloxane coating |
| US4732841A (en) * | 1986-03-24 | 1988-03-22 | Fairchild Semiconductor Corporation | Tri-level resist process for fine resolution photolithography |
| US4756977A (en) * | 1986-12-03 | 1988-07-12 | Dow Corning Corporation | Multilayer ceramics from hydrogen silsesquioxane |
| US4911992A (en) * | 1986-12-04 | 1990-03-27 | Dow Corning Corporation | Platinum or rhodium catalyzed multilayer ceramic coatings from hydrogen silsesquioxane resin and metal oxides |
| US4749631B1 (en) * | 1986-12-04 | 1993-03-23 | Multilayer ceramics from silicate esters | |
| US4753855A (en) * | 1986-12-04 | 1988-06-28 | Dow Corning Corporation | Multilayer ceramic coatings from metal oxides for protection of electronic devices |
| JPS63213347A (en) * | 1987-02-27 | 1988-09-06 | Mitsubishi Electric Corp | Semiconductor device |
| US4847162A (en) * | 1987-12-28 | 1989-07-11 | Dow Corning Corporation | Multilayer ceramics coatings from the ceramification of hydrogen silsequioxane resin in the presence of ammonia |
| IT1226701B (en) * | 1988-07-29 | 1991-02-05 | Eniricerche Spa | PROCEDURE FOR THE DEPOSITION OF ORGANOSILANS ON SILICON OR SILICON OXIDE SUBSTRATES FOR DEVICES OF THE EOS OR CHEMFET TYPE. |
| JPH02291129A (en) * | 1989-04-28 | 1990-11-30 | Nec Corp | Semiconductor device |
| DE9206834U1 (en) * | 1992-02-21 | 1993-06-17 | Robert Bosch Gmbh, 7000 Stuttgart, De | |
| JP2934353B2 (en) * | 1992-06-24 | 1999-08-16 | 三菱電機株式会社 | Semiconductor device and manufacturing method thereof |
| US5874367A (en) | 1992-07-04 | 1999-02-23 | Trikon Technologies Limited | Method of treating a semi-conductor wafer |
| DE69426208T2 (en) * | 1993-08-05 | 2001-05-17 | Matsushita Electronics Corp | Semiconductor component with capacitor and its manufacturing process |
| US5858880A (en) * | 1994-05-14 | 1999-01-12 | Trikon Equipment Limited | Method of treating a semi-conductor wafer |
| WO1998008249A1 (en) | 1996-08-24 | 1998-02-26 | Trikon Equipments Limited | Method and apparatus for depositing a planarized dielectric layer on a semiconductor substrate |
| TW437017B (en) * | 1998-02-05 | 2001-05-28 | Asm Japan Kk | Silicone polymer insulation film on semiconductor substrate and method for formation thereof |
| KR100661944B1 (en) * | 2000-05-22 | 2006-12-28 | 제이에스알 가부시끼가이샤 | Composition for Forming Film, Methods for Producing the Same, Methods for Forming Film and Silica Films |
| US7834119B2 (en) | 2002-04-18 | 2010-11-16 | Lg Chem, Ltd. | Organic silicate polymer and insulation film comprising the same |
| CN103030832B (en) | 2005-11-30 | 2015-07-08 | Lg化学株式会社 | Method for preparing microcellular foam of thermoplastic resin prepared with die having improved cooling property |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1347948A (en) * | 1961-12-15 | 1964-01-04 | Pacific Semiconductors | Process for esterification of silicon dioxide at atmospheric pressure |
| JPS5850417B2 (en) * | 1979-07-31 | 1983-11-10 | 富士通株式会社 | Manufacturing method of semiconductor device |
| JPS5760330A (en) * | 1980-09-27 | 1982-04-12 | Fujitsu Ltd | Resin composition |
-
1983
- 1983-07-14 CA CA000432475A patent/CA1204527A/en not_active Expired
- 1983-08-01 FR FR8312637A patent/FR2531811B1/en not_active Expired
- 1983-08-10 GB GB08321502A patent/GB2125423B/en not_active Expired
- 1983-08-10 BE BE0/211328A patent/BE897503A/en not_active IP Right Cessation
- 1983-08-11 JP JP58145809A patent/JPS5948929A/en active Pending
- 1983-08-11 DE DE19833329065 patent/DE3329065A1/en not_active Withdrawn
- 1983-08-12 IT IT22560/83A patent/IT1203708B/en active
- 1983-08-12 NL NL8302845A patent/NL8302845A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2531811B1 (en) | 1986-10-31 |
| GB2125423A (en) | 1984-03-07 |
| GB2125423B (en) | 1985-09-04 |
| IT1203708B (en) | 1989-02-15 |
| DE3329065A1 (en) | 1984-02-16 |
| NL8302845A (en) | 1984-03-01 |
| GB8321502D0 (en) | 1983-09-14 |
| IT8322560A0 (en) | 1983-08-12 |
| BE897503A (en) | 1983-12-01 |
| JPS5948929A (en) | 1984-03-21 |
| FR2531811A1 (en) | 1984-02-17 |
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