Low temperature ALD SiO2

0001The present invention relates to methods for depositing silicon dioxide by atomic layer deposition (ALD).

0002In the field of semiconductor processing, flat-panel display processing or other electronic device processing, vapor deposition processes have played an important role in depositing materials onto substrates. As the geometries of electronic devices continue to shrink and the density of devices continues to increase, the size and aspect ratio of the features are becoming more aggressive. Accordingly, conformal deposition of materials to form these devices is becoming increasingly important.

0003While conventional chemical vapor deposition (CVD) has proved successful for device geometries and aspect ratios down to about 0.15 µm, the more aggressive device geometries require an alternative deposition technique. One technique that is receiving considerable attention is ALD. During an ALD process, reactant gases are sequentially introduced into a process chamber containing a substrate. Generally, a first reactant is pulsed into the process chamber and is adsorbed onto the substrate surface. A second reactant is then pulsed into the process chamber and reacts with the first reactant to form a deposited material. A purge step may be carried out between the delivery of each reactant gas. The purge step may be a continuous purge with a carrier gas or a pulse purge between the delivery of the reactant gases.

0004The formation of silicon dioxide by ALD is a process that is known in the art. In forming silicon dioxide by ALD, a silicon precursor may be pulsed into the chamber followed by an oxidizing source. When water is used as the oxidizing source, the ALD process typically requires a high temperature and a longer exposure time due to the moderate reactivity of water.

0005Therefore, there is a need in the art for a method and apparatus for depositing silicon dioxide using water in an ALD at a low temperature.

0006The aforementioned problems are at least partly solved by a silicon dioxide deposition method as laid out in claim 1, a silicon dioxide deposition method as laid out in claim 11 and a silicon dioxide deposition method as laid out in claim 20. Further aspects, details, features and embodiments are evident from the dependent claims, the description and the accompanying drawings.

0007The present invention generally comprises a silicon dioxide ALD method. By providing pyridine as a catalyst, water may be utilized as the oxidization source while depositing at a low temperature. Prior to exposing the substrate to the water, the substrate may be exposed to a pyridine soak process. Additionally, the water may be co-flowed to the chamber with the pyridine through separate conduits to reduce interaction prior to entering the chamber. Alternatively, the pyridine may be co-flowed with a silicon precursor that does not react with pyridine.

0008In one embodiment, the invention comprises a silicon dioxide deposition method comprising positioning a substrate in a chamber, exposing the substrate to a silicon precursor, exposing the substrate to a pyridine soak, and exposing the substrate to an oxidizing source.

0009In another embodiment, the invention comprises a silicon dioxide deposition method comprising positioning a substrate in a chamber, exposing the substrate to a silicon precursor, and exposing the substrate to an oxidizing source and pyridine, the pyridine and the oxidizing source flowing into the chamber through separate inlets.

0010In yet another embodiment, the invention comprises a silicon dioxide deposition method comprising positioning a substrate in a chamber, exposing the substrate to hexachlorodisilane, and exposing the substrate to H₂O and pyridine, the pyridine and H₂O flowing into the chamber through separate inlets.

0011So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the invention and are described in the following:

0012Figure 1A is a schematic representation of an apparatus 100 according to one embodiment of the invention.

0013Figure 1B is a schematic representation of injector plenums 108a-c according to one embodiment of the invention.

0014Figure 2 is a flow chart 200 of a deposition method according to one embodiment of the invention.

0015Figure 3 is a flow chart 300 of a deposition method according to another embodiment of the invention.

0016Figure 4 is a flow chart 400 of a deposition method according to yet another embodiment of the invention.

0017Figure 5 is a flow chart 500 of a deposition method according to still another embodiment of the invention.

0018To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.

0019The present invention generally comprises a silicon dioxide ALD method. By providing pyridine as a catalyst, water may be utilized as the oxidization source while depositing at a low temperature. Prior to exposing the substrate to the water, the substrate may be exposed to a pyridine soak process. Additionally, the water may be co-flowed to the chamber with the pyridine through separate conduits to reduce interaction prior to entering the chamber. Alternatively, the pyridine may be co-flowed with a silicon precursor that does not react with pyridine.

0020Figure 1A is a schematic representation of an apparatus 100 according to one embodiment of the invention. The apparatus 100 comprises a vacuum chamber 102. The apparatus 100 may be a batch apparatus 100 that may contain one or more susceptors 106 upon which a substrate 104 may be placed. In one embodiment, the apparatus 100 may be a single substrate 104 apparatus. It is beneficial to process more than one substrate 104 simultaneously in order to increase throughput. One challenge posed with batch processes is maintaining a wafer to wafer uniformity.

0021Precursors may be fed to the apparatus 100 through an injector plenum 108. The injector plenum 108 may comprise a plenum wall 110 and an injection plate 114 that together surround and define an injection plenum chamber 122. The injection plate 114 has a plurality of holes 116 through which the precursor gas, purge gas, and carrier gas may flow 120 into the vacuum chamber 102. The injection plate 114 separates the injector plenum 108 from the vacuum chamber 102 so that the vacuum chamber 102 is the low pressure side 112 of the injector plenum 108. The precursors, purge gas, and carrier gas may be introduced to the injector plenum 108 through conduits 118a-118c.

0022The apparatus 100 may be exhausted through an exhaust plenum 124. The exhaust plenum may comprise an exhaust plate 126 and a plenum wall 130 that enclose and define an exhaust plenum chamber 128. A plurality of holes 132 may be present in the exhaust plate 126. The gases are exhausted from the exhaust plenum 124 through the exhaust port 136.

0023Additional gas may be introduced to the exhaust plenum 124 through conduit 134. The additional gas may abate or convert reaction by-products that may otherwise condense on surfaces of the exhaust plenum 124 and the vacuum chamber 102. A throttle valve 138 may control the vacuum chamber 102 pressure.

0024When forming silicon dioxide by ALD, a silicon precursor may be delivered to the apparatus 100. Exemplary silicon precursors useful for depositing silicon-containing materials include silanes, alkylsilanes, aminosilanes, alkylaminosilanes, silanols, or alkoxy silanes. For example, silicon precursors may include (Me₂N)₄Si, (Me₂N)₃SiH, (Me₂N)₂SiH₂, (Me₂N)SiH₃, (Et₂N)₄Si, (Et₂N)₃SiH, (MeEtN)₄Si, (MeEtN)₃SiH, Si(NCO)₄, MeSi(NCO)₃, SiH₄, Si₂H₆, SiCl₄, Si₂Cl₆, MeSiCl₃, HSiCl₃, Me₂SiCl₂, H₂SiCl₂, MeSi(OH)₃, Me₂Si(OH)₂, (MeO)₄Si, (EtO)₄Si, or derivatives thereof. Other alkylaminosilane compounds useful as silicon precursors include (RR'N)_4-nSiH_n, where R or R' are independently hydrogen, methyl, ethyl, propyl or butyl and n = 0-3. Other alkoxy silanes may be described by the generic chemical formula (RO)_4-nSiL_n, where R = methyl, ethyl, propyl or butyl and L = H, OH, F, Cl, Br or I and mixtures thereof. Also, higher silanes may be used as silicon precursors within some embodiments of the invention. Higher silanes are disclosed in commonly assigned United States Patent Publication No. <patcit id="pcit0001" dnum="US20040224089A1"><text>US 2004/0224089 A1</text></patcit>, which is incorporated herein by reference in its entirety. In some embodiments, the silicon precursor may comprise tris(dimethylamino)silane ((Me₂N)₃SiH or Tris-DMAS), tetrakis(dimethylamino)silane ((Me₂N)₄Si or TDMAS) or other dialkylaminosilanes, while in other embodiments the silicon precursor may comprise silane (SiH₄). In yet another embodiment, the silicon precursor may comprise hexachlorodisilane (HCDS).

0025The oxidizing source for forming silicon dioxide in an ALD process may comprise oxygen (O₂), ozone (O₃), atomic-oxygen (O), hydrogen peroxide (H₂O₂), nitrous oxide (N₂O), nitric oxide (NO), dinitrogen pentoxide (N₂O₅), nitrogen dioxide (NO₂), water (H₂O), derivatives thereof or combinations thereof. In the exemplified embodiments, the oxidizing source comprises water (H₂O).

0026When using water as the oxidizing source, a catalyst is supplied to allow the ALD to proceed at a faster rate and a lower temperature than occurs in absence of the catalyst. Examples of catalysts that may be used include ammonia and pyridine. Pyridine and water may interact. Therefore, when water and pyridine are co-flowed together through the same input conduit to the chamber, the water and pyridine may interact prior to reaching the chamber. When the water and the pyridine interact, the pyridine no longer effectively functions as a catalyst and hence, the ALD deposition rate is not increased.

0027To prevent water and pyridine interaction prior to reaching the chamber, pyridine and water may be co-flowed to the chamber using separate feed conduits to separate injector plenums. Figure 1B is a schematic representation of injector plenums 108a-c according to one embodiment of the invention. As shown in Figure 1B, each conduit 118a-118c is fed to a separate injector plenum 108a-108c. Thus, pyridine-water interaction may be prevented until the pyridine and water reach the chamber.

0028Silicon precursors such as HCDS do not interact with pyridine. Therefore, the silicon precursor and the pyridine may be co-flowed to the chamber using the same conduit and injector plenum. In one embodiment, the pyridine and the silicon precursor may be flowed to the chamber using the same conduit and injector plenum. In another embodiment, the pyridine and the silicon precursor may be flowed to the chamber using separate conduit and injector plenums.

0029An alternative to co-flowing pyridine and water to the chamber using separate injector plenums and conduit is to expose the substrate to a pyridine soak prior to introducing the water to the chamber. A pyridine soak may comprise exposing the substrate to pyridine without introduction of other precursors or oxidizers such as water. The substrate may be exposed to the pyridine for a time sufficient to saturate the substrate with pyridine. In one embodiment, the pyridine soak occurs for greater than about 10 seconds. By performing a pyridine soak, sufficient catalyst may be present within the chamber and at the substrate surface to ensure that catalyst is present when the water precursor is introduced. Because the pyridine is already in the chamber, all of the pyridine may not be consumed by interacting with the water prior to reaching the chamber. When a pyridine soak is performed, additional pyridine may be co-flowed with the oxidizer and with the silicon precursor. In one embodiment, a pyridine soak is performed and continues to flow into the chamber as the silicon precursor and subsequently the water is delivered to the chamber. In another embodiment, the pyridine soak is performed and pyridine delivery is stopped during water delivery and silicon precursor delivery. The pyridine allows the reaction to occur at low temperatures such as from about room temperature to about 160 degrees Celsius. In one embodiment, the temperature is about 75 degrees Celsius.

0030Figure 2 is a flow chart 200 of a deposition method according to one embodiment of the invention. Initially, one or more substrates may be placed into the process chamber (Step 210). The substrates may then be exposed to a pyridine soak (Step 220). The pyridine soak may occur for at least 10 seconds. Following the pyridine soak, a pulse of HCDS may be introduced to the chamber while the pyridine continues to flow into the chamber (Step 230). Alternatively, the pyridine flow may be stopped after the pyridine soak and then pulsed into the chamber with the HCDS.

0031Following the pulse of HCDS, the chamber may be purged by introducing a purge gas into the chamber (Step 240). Exemplary purge gases that may be used include inert gases such as argon. In one embodiment, the purge gas may comprise nitrogen. The chamber may be pumped to remove the purge gas and any remaining HCDS and pyridine that may be present in the chamber. In one embodiment, the pumping is not performed so that only a purging step is performed. Alternatively, the purge step may be eliminated so that the chamber is pumped to remove the HCDS and the pyridine. In one embodiment, the pumping may occur both before and after the purge gas introduction. In another embodiment, both the purging and the pumping may be repeated. The pumping and/or purging may occur a plurality of times. In yet another embodiment, the purging and the pumping may be combined into one step.

0032Following the pumping and/or purging, the substrate may be exposed to a second pyridine soak (Step 250). The second pyridine soak may occur under the same processing conditions present for the first pyridine soak discussed above. Following the pyridine soak, a pulse of H₂O may be introduced to the chamber while the pyridine continues to flow into the chamber (Step 260). Alternatively, the pyridine flow may be stopped after the pyridine soak and then pulsed into the chamber with the H₂O. Because pyridine is already present within the chamber from the soak step, sufficient pyridine is present to act as a catalyst. Following the exposure of the substrate to H₂O, a second pumping and/or purging cycle (Step 270) may be performed under conditions as discussed above.

0033After the chamber has been pumped and/or purged, the thickness of the SiO₂ layer may be measured to determine if the predetermined thickness of SiO₂ has been reached (Step 280). If the predetermined thickness has not been reached, the deposition sequence may be repeated. If the predetermined thickness has been reached, then the process ends (Step 290).

0034Figure 3 is a flow chart 300 of a deposition method according to another embodiment of the invention. Initially, one or more substrates may be placed into the process chamber (Step 310). The substrates may then be exposed to a pyridine soak (Step 320). The pyridine soak may occur for at least 10 seconds. Following the pyridine soak, a pulse of HCDS may be introduced to the chamber while no pyridine is delivered to the chamber (Step 330). Alternatively, the pyridine flow may be stopped after the pyridine soak and then pulsed into the chamber with the HCDS or the pyridine may continue to be delivered.

0035Following the pulse of HCDS, the chamber may be purged and/or pumped as discussed above (Step 340). Following the pumping and/or purging, the substrate may be exposed to a second pyridine soak (Step 350). The second pyridine soak may occur under the same processing conditions present for the first pyridine soak discussed above. Following the pyridine soak, the pyridine flow may be stopped and a pulse of H₂O may be introduced to the chamber (Step 360). Following the exposure of the substrate to H₂O, a second pumping and/or purging cycle (Step 370) may be performed under conditions as discussed above.

0036After the chamber has been pumped and/or purged, the thickness of the SiO₂ layer may be measured to determine if the predetermined thickness of SiO₂ has been reached (Step 380). If the predetermined thickness has not been reached, the deposition sequence may be repeated. If the predetermined thickness has been reached, then the process ends (Step 390).

0037Figure 4 is a flow chart 400 of a deposition method according to yet another embodiment of the invention. Initially, one or more substrates may be placed into the process chamber (Step 410). The substrates may then be exposed to a pulse of HCDS and pyridine (Step 420). Following the pulse of HCDS and pyridine, the chamber may be purged by introducing a purge gas into the chamber (Step 430) in a manner as described above.

0038Following the pumping and/or purging, the substrate may be exposed to simultaneous pulses of H₂O and pyridine (Step 440). The H₂O and the pyridine may be co-flowed through different conduit lines and into the chamber through different inlets. By utilizing different conduits and different inlets, the H₂O and pyridine may not be exposed to each other until they reach the chamber. If the pyridine and the H₂O are co-flowed through the same conduit, the pyridine and the H₂O may interact prior to reaching the chamber. When the H₂O and the pyridine interact prior to entering the chamber, the effectiveness of the pyridine as a catalyst may be reduced so as to render the catalyst useless.

0039Following the exposure of the substrate to H₂O, a second pumping and/or purging cycle (Step 450) may be performed under conditions as discussed above. After the chamber has been pumped and/or purged, the thickness of the SiO₂ layer may be measured to determine if the predetermined thickness of SiO₂ has been reached (Step 460). If the predetermined thickness has not been reached, the deposition sequence may be repeated. If the predetermined thickness has been reached, then the process ends (Step 470).

0040Figure 5 is a flow chart 500 of a deposition method according to still another embodiment of the invention. Initially, one or more substrates may be placed into the process chamber (Step 510). The substrates may then be exposed to a pyridine soak (Step 520). The pyridine soak may occur for at least 10 seconds. Following the pyridine soak, a pulse of HCDS may be introduced to the chamber while the pyridine continues to flow into the chamber (Step 530). Alternatively, the pyridine flow may be stopped after the pyridine soak and then pulsed into the chamber with the HCDS. Following the pulse of HCDS, the chamber may be purged and/or pumped as described above (Step 540).

0041Following the pumping and/or purging, the substrate may be exposed to a second pyridine soak (Step 550). The second pyridine soak may occur under the same processing conditions present for the first pyridine soak discussed above. Following the pyridine soak, a pulse of H₂O may be introduced to the chamber while the pyridine continues to flow into the chamber (Step 560). Alternatively, the pyridine flow may be stopped after the pyridine soak and then pulsed into the chamber with the H₂O. In one embodiment, the pyridine and the H₂O are fed through separate conduits as discussed above in relation to Figure 4. Following the exposure of the substrate to H₂O, a second pumping and/or purging cycle (Step 570) may be performed under conditions as discussed above.

0042After the chamber has been pumped and/or purged, the thickness of the SiO₂ layer may be measured to determine if the predetermined thickness of SiO₂ has been reached (Step 580). If the predetermined thickness has not been reached, the deposition sequence may be repeated. If the predetermined thickness has been reached, then the process ends (Step 590).

0043It should be understood that when reference is made to processing a substrate, multiple substrates may be processed. For example, about 2 substrates, about 25 substrates, about 50 substrates, or about 100 substrates may be processed in a batch chamber. Additionally, the pyridine soak may occur for a time period of about 1 second to about 90 minutes or about 1 minute to about 20 minutes. Alternatively, the pyridine soak may occur for about 30 seconds to about 60 minutes or about 20 minutes to about 40 minutes. In still another alternative, the pyridine soak may occur for about 1 minute to about 40 minutes.

0044By providing a pyridine soak and/or co-flowing pyridine and H₂O through separate conduit lines, sufficient pyridine reaches the chamber and hence, the substrate surface, to ensure that pyridine acts as a catalyst. By utilizing pyridine as a catalyst in an H₂O oxidizing atmosphere, SiO₂ ALD may occur at an increased rate below 160 degrees C.

0045While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

0046The invention is also directed to an apparatus for carrying out the disclosed methods and including apparatus parts for performing each described method steps. These method steps may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, the invention is also directed to methods by which the described apparatus operates. It includes method steps for carrying out every function of the apparatus.