Patent ID: 12243742

DETAILED DESCRIPTION

A substrate processing method according to this disclosure provides methods to adjust a stress of a film and prevent and/or suppress a substrate deformation or film peeling-off occurred due to the stress of a film or a substrate.

FIG.2is a process flow according to one embodiment and the details ofFIG.2is described as follows.Loading a substrate (101): A substrate may be loaded onto a substrate support in the reaction space. The substrate support supports the substrate and provides a heat energy to the substrate to keep the substrate temperature at designated temperature.Forming a first film (201): A first film may be formed on the substrate by supplying a first reactant and a second reactant alternately and sequentially to the substrate. The first reactant may be a precursor containing a Si element and the second reactant may be activated by radio frequency power. The second reactant may not chemically react with the first reactant. For example, the first reactant may be an aminosilane precursor. The second reactant may be inactive gas such as Ar or He or a combination thereof. In this step, the first reactant may be dissociated and broken by plasma, and adsorbed onto the substrate. Since there may be no chemical reaction between the first reactant and the second reactant, the film adsorbed onto the substrate may comprise fragments of the dissociated or broken first reactant molecules, e.g. silicon (Si), carbon (C), nitrogen (N), chlorine (Cl), iodine (I), alkyl group ligand (e.g. CnH2n+1) and hydrogen (H) fragments and/or the mixture thereof. A first layer of the first film may be chemisorbed to the substrate. The second layer may be deposited over the first film and may comprise a stack of those fragments. The first film may be densified by the activated second gas. Also, the activated second gas may contribute to the dissociation of the first gas. This first step may be repeated “M” times.Conversion of the first film into a second film (301): A third reactant may be supplied to the first film formed on the substrate. The third reactant may be activated by radio frequency power and chemically reacts to the first film. The third reactant may be oxygen-containing gas, more preferably the third reactant may be oxygen. In this step, the first film may be converted into a second film. Since the activated third reactant chemically reacts to the first film, the first film may be converted into the second film. The second film, for example, may be SiO2film. This second step may be repeated “N” times.

InFIG.2, a cycle ratio of first step201to second step301may be larger than 5, preferably larger than 20 or more preferably larger than 50. For example, the first step201may be repeated 50 times and the second step301may be repeated one time. Further, the first step201and the second step301may be repeated “X” times, at least one time as a group cycle or super-cycle to more facilitate the conversion of the first film into the second film as the first film thickness increases.

FIG.3is a schematic view of the process flow ofFIG.2. A first step and a second step ofFIG.3correspond to a first step201, a second step301ofFIG.2respectively. In first step ofFIG.3, a first layer may be formed by supplying a first reactant and a second reactant sequentially and alternately. A second reactant may be activated by a radio frequency power, for example.

In another embodiment a second reactant may be supplied continuously as shown inFIG.3. InFIG.3, the first step may be repeated “M” times, at least one time, followed by the second step. In second step ofFIG.3, a third reactant may be supplied and activated by plasma and the second step may be repeated “N” times, at least one time. The cycle ratio of the first step and the second step, that is M/N, may be larger than 5, preferably larger than 20 or more preferably larger than 50. The activated third reactant may convert the first film into the second film. For example, the first reactant may be a Si-containing precursor, the second reactant may be Ar and the third reactant may be oxygen. The Si-containing precursor as the first reactant may be at least one of DIPAS, SiH3N(iPr)2; TSA, (SiH3)3N; DSO, (SiH3)2; DSMA, (SiH3)2NMe; DSEA, (SiH3)2NEt; DSIPA, (SiH3)2N(iPr); DSTBA, (SiH3)2N(tBu); DEAS, SiH3NEt2; DTBAS, SiH3N(tBu)2; BDEAS, SiH2(NEt2)2; BDMAS, SiH2(NMe2)2; BTBAS, SiH2(NHtBu)2; BITS, SiH2(NHSiMe3)2; TEOS, Si(OEt)4; SiCl4; HCD, Si2Cl6; 3DMAS, SiH(N(Me)2)3; BEMAS, Si H2[N(Et)(Me)]2; AHEAD, Sit (NHEt)6; TEAS, Si(NHEt)4; Si3H8; DCS, SiH2Cl2; SiHI3; SiH2I2or mixture thereof. The oxygen gas as the third reactant may be at least one of O2, O3, CO2, H2O, NO2and N2O or mixture thereof.

The first film may be a stack of fragments of Si precursor molecules densified by plasma and may be converted into SiO2as the second film by oxygen plasma. In other words, the step1may be a source coating step and the step2may be an oxygen treatment step. InFIG.3, a plasma condition of step2may vary. For example, a radio frequency power may be provided in pulse with a certain duty ratio to reduce a damage to the substrate or sublayer.

When the radio frequency power is provided in pulse, the ratio of the actual radio frequency power supply time b to the unit cycle time a of radio frequency pulsing, that is b/a, is defined as a duty ratio as shown inFIG.4. In another embodiment according to this inventive concept, the radio frequency power may be provided in pulse with a range of duty ratio of 10% to 75%.

FIG.5is another embodiment according to the inventive concept. In first step a plasma may be supplied in continuous mode, but in second step a plasma may be supplied in pulse mode with certain duty ratio. But supplying a plasma in pulse is not limited thereto. In another embodiment, a plasma may be supplied in pulse to at least one of the first step and the second step.

Table 1 is an experimental condition of one embodiment according toFIG.3in which plasma may be supplied in continuous mode in which plasma may not be supplied in pulse.

TABLE 1an experimental condition of one embodimentItemsConditionsProcess temperature (° C.)room temperature to 150° C. (preferably 50 to 150° C.)Process pressure (Torr)1.0 to 5.0 Torr (preferably 2.0 to 3.0 Torr)Si precursorDIPAS (diisopropylaminosilane)ReactantO2Purge gasArFirst step @ forming a first filmProcessSource feed(S1)0.05 to 2.0 sec. (preferably 0.1 to 1.0 sec.)time (sec)Source purge(S2)0.05 to 2.0 sec. (preferably 0.1 to 1.0 sec.)Plasma-on(S3)0.05 to 2.0 sec. (preferably 0.1 to 1.0 sec.)Purge(S4)0.05 to 2.0 sec (preferably 0.1 to 1.0 sec)S1~S4 cycle50 to 200 cycles (preferably 100 to 150 cycle)Gas flowSource carrier Ar100 to 10,000 sccm (preferably 600 to 1,200 sccm)rate (sccm)Purge Ar1,000 to 10,000 sccm (preferably 3,000 to 6,000 sccm)PlasmaRF power(W)100 to 1,000 W (preferably 200 to 400 W)conditionRF frequency13 to 100M Hz (preferably 27 to 60 MHz)Second step@ conversion of the first film into the second filmProcessPre purge(S5)0.05 to 5.0 sec(preferably 0.5 to 5.0 sec)time (sec)Plasma-on(S6)0.05 to 3.0 sec(preferably 0.1 to 2.0 sec)Purge(S7)0.05 to 2.0 sec(preferably 0.1 to 1.0 sec)S5~S7 cycle1 to 10 cycle(preferably 1 to 5 cycle)Gas flowReactant(O2)50 to 1000 sccm(preferably 200 to 500 sccm)rate (sccm)Purge Ar1,000 to 10,000 sccm(preferably 3,000 to 6,000 sccm)PlasmaRF power(W)100 to 1,000 W(preferably 200 to 500 W)conditionRF frequency13 to 100 MHz(preferably 27 to 60 MHz)

FIG.6shows a film stress in accordance with the cycle ratio of a first step and a second step. InFIG.6, a SiO2film formed at room temperature by normal process in which Si-containing precursor and oxygen plasma are provided alternately and sequentially to form SiO2film may have a tensile stress of 109.8 MPa, but the SiO2film stress according to this inventive concept may vary in accordance with the cycle ratio of the first step and the second step.

In first step a Si-containing precursor as a first reactant and Ar plasma as a second reactant may be alternately and sequentially provided to the substrate to form a first film consisted of fragments of elements and/ligands of dissociated Si precursor.

In second step, an oxygen plasma as a third reactant may be provided to the first film to convert the first film into SiO2film as a second film. In one embodiment, a cycle ratio of the first step to the second step may be 50. For example, the first step may be 50 cycles and the second step may be one cycle. In another embodiment, a cycle ratio of the first step to the second step may be 100. For example, the first step may be 100 cycles and the second step may be one cycle.

FIG.7shows a film composition after carrying out the first step and the second step. As shown inFIG.7, SiO2films formed under the cycle ratio of 50:1 and 100:1 conditions ofFIG.6, for example, have stoichiometric SiO2film compositions without other elements coming from fragments of nitrogen, carbon and hydrogen or mixture thereof. This means the first film may be substantially converted into the second film by oxygen plasma as a third reactant.

As shown inFIG.6, a film stress of the first film has a compressive stress of −74.8 MPa, but as the oxygen plasma is provided and the first film is converted into the second film, a film stress is turned into a tensile stress. Also the higher the cycle ratio of the step1to the step2is, the higher the tensile stress of SiO2film is. That is, SiO2film stress may be properly adjusted by controlling the cycle ratio of the first step and the second step. So, the optimal process condition or the cycle ratio may be set to prevent a substrate deformation and film peeling-off, e.g. warpage, crack, etc. So a film with targeted stress may be formed by controlling the cycle ratio.

In another embodiment this process may be carried out to introduce a stress control film. For instance, if a substrate is processed at high temperature in a reactor, undergoing a compressive or a tensile stress, then the substrate may be deformed or broken, or film peeling-off or crack in it may occur. In this case, a stress control film may be introduced to the backside of the substrate to offset a compressive or a tensile stress of the substrate. The stress control film may be a film with a compressive stress or a tensile stress formed by a method in accordance with aforementionedFIG.2andFIG.3before processing a substrate That is, a stress of the stress control film may offset a stress of the substrate by adjusting the cycle ratio of the source coating step and the plasma treatment step. So the stress control film may suppress a substrate deformation and cracks in a film on the substrate during processing a substrate at high temperature.FIG.8shows a process flow introducing a stress control film.

InFIG.8, a first film may be formed on the backside of the substrate by supplying a first reactant and a second reactant in a first step. Then the first film may be converted into a second film by supplying a third reactant in a second step. A stress of the second film may be adjusted by controlling the cycle ratio of the first step and the second step, and the second film may act as a stress control film. The process sequence is described inFIG.2andFIG.3in more detail, so the detailed description of it is omitted herein. Then a third film may be formed on the front side of the substrate. After the process is completed, the stress control film, that is, the second film may be removed by a fluorine-containing etchant such as CF4. By carrying out this process, deformation or break of the substrate and cracks or damages in the third film may be suppressed.

The process ofFIG.8may be performed ex-situ. For example, this process may be carried out in a chamber with a plurality of reactor in it. For example, the substrate may be processed by being transferred sequentially from one reactor to another to carry out each step ofFIG.8.

FIG.9shows embodiments ofFIG.8. InFIG.9A, a second film or a stress control film2may be formed on the backside of the substrate1at low temperature, e.g. room temperature. Then a targeted third film3may be formed on the front side of the substrate1at high temperature. A stress of the substrate may be offset by introducing a stress control film with a compressive stress or a tensile stress to the backside of the substrate1.

InFIG.9Aa tensile stress of the substrate may be offset by forming a stress control film2with compressive stress on the backside of the substrate1, so deformation or break of the substrate or cracks in a third film3on the substrate may be suppressed.

InFIG.9Ba compressive stress of the substrate may be offset by forming a stress control film2with tensile stress on the backside of the substrate1, so deformation or break of the substrate or cracks in a third film3on the substrate may be suppressed.

Controlling a film stress by converting one film into another one at low temperature provides another technical benefit. A SiO2hardmask may be used in patterning process of semiconductor device fabrication. But as the device shrinkages, a film thickness on the device becomes thinner and a thermal budget becomes a serious problem since it causes a sublayer damage, abnormal migration of electrons across the structures of the device and malfunction of the device. So a SiO2hardmask process at low temperature may be required with the same film properties as the one formed at the existing high temperature process. So the inventive concept according to this invention may provide a solution to it.

FIG.10shows a process flow for forming a hardmask on patterns of the substrate according to another embodiment.

In the first step101ofFIG.10, a substrate with pattern structure may be loaded to a substrate support. In the second step301ofFIG.10, a first film may be formed on the pattern of the substrate. The first film may be formed in accordance with the aforementioned method inFIG.2andFIG.3, so detailed description will be omitted herein. After the second step301, the first film may be converted into a second film in the third step501. The conversion of the first film into the second film may be carried out in accordance with the aforementioned method inFIG.2andFIG.3, so detailed description will be omitted herein.

FIG.11shows a wet etch ratio (WER) of SiO2film formed in accordance withFIG.10and the existing method. The wet etch rate is carried out in hydrofluoric acid (HF) diluted in the ratio of 100:1 in deionized water (DIW).

InFIG.11details of each process condition are described as below.A: SiO2film formed by normal PEALD method at 50° C. in which DIPAS (diisopropylaminosilane) precursor and oxygen plasma may be alternately and sequentially provided.B: Precursor deposition. Si-containing film may be formed at 50° C. by supplying DIPAS silicon precursor and Ar plasma alternately and sequentially.C: SiO2film formed at 50° C. by carrying out 50 cycles of alternate and sequential supply of DIPAS precursor and Ar plasma and one cycle of oxygen plasma to convert into SiO2film.D: SiO2film for hardmask application formed at 300° C. by normal PEALD method in which DIPAS precursor and oxygen plasma may be alternately and sequentially provided.

As shown in A ofFIG.11, SiO2film formed at 50° C. by normal PEALD method has high wet etch rate of 175.84 Å/min, in other words, low wet etch resistance. But in B condition a Si-containing film formed at 50° C. by supplying DIPAS precursor and Ar plasma has very low WER, in other words, high wet etch resistance. But as shown in C, oxygen treatment and a resultant conversion of Si-containing film into SiO2film at 50° C. increases the WER closer to that of SiO2film formed at 300° C. shown in condition D. In another embodiment, the WER of SiO2film formed at 50° C. may be almost the same as that of SiO2film formed at 300° C. or above by further controlling the cycle ratio of the first step and the second step. In other words, by adjusting the cycle ratio of the precursor deposition step and the plasma treatment step, film properties that may be achieved at high temperature, e.g. 300° C. or above may be achieved at low temperature, reducing a thermal budget to a device. So the inventive concept of this invention may provide a solution to the requirement for low temperature process.FIG.11also shows that films with different wet etch rates may be realized at low temperature by adjusting the cycle ratio of the precursor deposition step and the plasma treatment step, and this may make various applications available.

Controlling a film stress by converting one film into another one may provide another technical benefit in gap fill process. InFIG.12, a film1covering a top surface may be peeled off due to film stress, e.g. tensile stress as shownFIG.12A. But introducing a stress control film to the top surface of the film may suppress the film peeling-off as shownFIG.12B.

InFIG.12B, a gap is filled with a first film1and a second film or a stress control film2may be formed by supplying a first reactant and a second reactant activated by plasma in a first step, and the second film may be converted into a third film3in a second step. A stress of the third film3may be adjusted by controlling the cycle ratio of the first step and the second cycle. The details of the process is aforementioned inFIG.2andFIG.3, so detailed description of it will be omitted herein.

FIG.13shows a process flow ofFIG.12in which a substrate with gap structure may be loaded at step101, followed by filling the gap with a first film at step301. A second film may be formed on the first film at step501, followed by being converted into a third film at step701.