TW201642342A - Method for etching multilayered material layer by using plasma - Google Patents

Abstract

A method for etching a multilayered material layer by using plasma is disclosed. The multilayered material layer includes alternately laminated a first material layer and a second material layer. The etching method comprises performing a main etching step, which is to simultaneously inject first etching gas and second etching gas into a reaction chamber for etching the multilayered material layer until a through hole formed by etching reaches a first depth so as to switch into a middle processing step; and performing the middle processing step, which is to inject one of the first etching gas and the second etching gas to the reaction chamber for etching the multilayered material layer in order to correct a shape of a bottom portion of the through hole, in which after completing the correction of the shape of the bottom portion of the through hole, the main etching step is performed once again. Wherein, an etching selectivity ratio of the first etching gas to the first material layer and the second material layer is greater than 5.

Description

Method for etching multilayer materials by using plasma

The present invention relates to the field of plasma etching, and more particularly to an etching method for deep hole etching of a multilayer material layer formed by alternately laminating yttrium oxide and tantalum nitride.

Precision processing of semiconductor devices such as etching is usually performed by plasma etching. During the etching process, the substrate to be processed needs to be placed in a vacuum plasma reaction chamber, and then the reaction gas is introduced, and a high frequency (13.56/27/60 MHz) RF power source is simultaneously applied. The generated RF power is fed between the upper and lower electrodes of the plasma reaction chamber to generate a plasma of sufficient concentration. In order to control the energy of the charged ions to be incident perpendicularly to the substrate, a low frequency (2 MHz) RF power needs to be applied to the lower electrode in the reaction chamber. During the etching process, the reactive gas reacts with the material to be etched which is not covered by the mask layer to form a downwardly extending through hole, and the polymer component in the reaction gas forms a sufficiently thick polymer layer on the sidewall of the through hole. The side walls are such that they are not etched by the reaction gas in the horizontal direction. The polymer layer at the bottom of the through hole is bombarded by the vertically incident charged ions, so that the covering of the material to be etched at the bottom cannot be formed, and the reaction gas can continue to be etched downward, eventually forming a vertical through hole having a directionality. With the development of information technology, a large amount of information requires inexpensive and reliable storage, and vertically arranged three-dimensional VNAND storage is now increasingly becoming the main choice for such large-scale low-cost storage. As shown in FIG. 1A, in the manufacturing process, the VNAND device first needs to alternately deposit a plurality of layers of the yttrium oxide material layer 101 and the tantalum nitride material layer 103 on the substrate 100, and then form a mask material having an etched pattern on the alternate structures. Layer 105, this alternating two-layer structure has now reached a two-layer structure of 24 to 48 layers, and it is possible to further increase the number of layers to 54 or 72 layers in order to improve the storage capacity in the future. This multilayered alternating structure can achieve thicknesses above 2.4 microns. Since the material layer to be etched is alternately stacked, the reactive gas that needs to be introduced during the etching process also needs to be selected to be able to etch the two material layers. The existing etching parameters are typically selected to be C4F6 (30 sccm) and C4F8 (30 sccm), Ar (100 sccm), CH2F2 (50 sccm), O2 (60 sccm), and an etching duration of about 300 seconds. Among them, C4F8 and C4F6 have a faster etching rate for tantalum oxide, and a slower etching rate for tantalum nitride. CH2F2 etches faster for tantalum nitride and slower for tantalum oxide. Ar gas can be used as a gas molecule to bombard the bottom of the hole. The vias 102 formed after the etching is completed are filled into the conductor material as the extraction electrodes, and these electrodes are finally connected to an external data circuit to perform read and write operations on the VNAND memory.

In the process of etching the alternately stacked yttrium oxide material layer 101 and the tantalum nitride material layer 103, the above-mentioned gas component can ensure that the through hole extends vertically downward when the depth of the through hole 102 is not large, but when the through hole 102 is etched down to a certain extent At depth (such as 1um~2um depth), the positively charged particles continue to bomb down to the bottom. Since SiO and SiN are both insulating materials, these positive charges cannot be guided away, and the negatively charged particles cannot reach the through holes 102. The bottom and bottom are positively charged, so the sidewalls of the via 102 will generate charge buildup. A large amount of polymer gas in the reaction gas forms a protective layer on the sidewalls of the via holes, and these protective layers may cause uneven charges accumulated on the sidewalls due to uneven thickness, and these unevenly distributed positive charges may cause downward incidence of positive charges. The particles are deflected in the direction of long-distance flight, and the etching direction of the through-holes 102 is also shifted. As shown in Figure 1A, when the positive charge on the left side is more than the positive charge on the right side, the Ar+ particles will shift to the right, and the bottom of the via hole 102 will begin to show asymmetric etching. The left side wall of the bottom of the via hole starts to the right due to less material being etched away. Extended, the right offset is not obvious. However, if the charge accumulation problem is not solved, the charge of these asymmetric distributions will increase the degree of distortion of the via hole 102, eventually forming a curved hole as shown in FIG. 1B. In the subsequent conductive material filling step, such a through-hole having a curved topography makes it impossible for the conductive material to enter the underlying curved hole, which may result in the formation of the final electrode and the failure of the storage device.

In order to solve the above problems, the prior art proposes many methods such as a pulsed RF electric field, a pulsed inflowing gas, etc. to solve the problem of uneven distribution of charge and neutralization of the bottom positive charge, but due to the large depth of the via hole and the properties of the etched material. Restricting existing methods can only somehow slow down the degree of distortion and cannot completely solve the problem.

The invention solves the problem that the two alternating layers of insulating material are offset in the direction of the through hole during the deep hole etching process, and the invention proposes a method for etching the multilayer material layer by using the plasma, the multilayer material layer comprising multiple layers alternately stacked a first material layer and a second material layer, the etching method comprising: placing a substrate to be etched to the reaction chamber, including a plurality of material layers above the substrate, and a mask layer having an etched pattern over the plurality of material layers; performing a main etching step, Simultaneously etching the layer of the plurality of materials including the first etching gas and the second etching gas into the reaction chamber until the through hole formed by the etching reaches the first depth D, and switching to the intermediate processing step; performing the intermediate processing step, accessing the first An etching gas of one of the etching gas or the second etching gas is etched into the reaction chamber to etch the layer of the plurality of materials to correct the bottom morphology of the via hole, and the main etching step is performed again after correcting the bottom surface topography of the via hole; wherein the first etching gas is performed The first material layer and the second material layer have an etching selectivity ratio greater than 5, the second etching gas to the second material layer and the first material Etching selection ratio is greater than 5

In the performing the above intermediate processing step, the first etching gas may be introduced into the reaction chamber to etch the multi-layer material layer to correct the bottom shape of the through hole, and after completing the partial topography correction at the bottom of the through hole, the access is stopped. An etching gas is introduced into the reaction chamber through the second etching gas, and the main etching step is performed again after the bottom surface topography is corrected.

Wherein, the main etching step is performed again, so that the through hole depth is extended downward for a second time to reach 2D, and the intermediate processing step needs to be performed again to prevent the via hole shift phenomenon from occurring again. The intermediate processing step time is less than 40 seconds, and the length of the main etching step performed multiple times is greater than 200 seconds, and the time taken for the intermediate processing step does not significantly extend the overall processing time.

The etching selectivity ratio of the first etching gas to the first material layer and the second material layer is greater than 8, and the etching selectivity ratio of the second etching gas to the second material layer and the first material layer is also greater than 8.

Wherein, the first material layer is a layer of yttrium oxide material, the second material layer is a layer of tantalum nitride material, the first etching gas comprises a fluorocarbon compound, and the second etching gas comprises a fluorocarbon, wherein the fluorocarbon comprises C4F8 and C4F6 The fluorocarbon is CH2F2.

Wherein the multi-layer material layer comprises more than 48 layers of the first and second material layers, and the multi-layer material layer has a thickness greater than 3 microns.

Wherein, the first depth D is less than 2 microns, and the optimal first depth D may be selected to be greater than 1.5 microns and less than 2 microns.

The present invention is to solve the problem that the two layers of the alternately stacked insulating material are offset in the direction of the via hole during the deep hole etching process. The etched substrate of the present invention is deposited with a plurality of layers of insulating material alternately stacked, the insulating material layer further comprising a mask layer, and the mask layer is formed with a pattern for etching the through holes as a mask. The substrate to be etched is placed in the reaction chamber, and an etching gas is introduced, and high-frequency RF power (60 Mhz, power greater than 400 W) and high bias RF power (2 Mhz, power 5 K 10 10 kW) are applied to the electrodes in the reaction chamber. The substrate is etched.

The invention provides a method for etching a multilayer material by using a plasma. The main etching step is performed in an initial stage of etching. The main etching step uses the same main etching gas as the prior art, and the main etching gas system includes etching oxidation respectively. a first etching gas of germanium and a second etching gas for etching tantalum nitride and an auxiliary gas such as oxygen or argon. The reaction gas is continuously etched downward to form a through hole of a certain depth, and the etching hole starts to appear or the transition of the main etching gas is stopped when the offset phenomenon as shown in FIG. 1A is predicted, and the intermediate processing step is entered. The depth of the sidewall shape distortion of the etched via 102 is affected by specific parameters such as etching gas composition, radio frequency power, and gas pressure. According to the inventors, it is possible to detect the sidewall distortion significantly when the multilayer material layer which is alternately laminated by continuous etching reaches a depth of about 1.5 to 2 um, so that it is possible to select the time point at which the main etching step is stopped to enter the intermediate processing step according to the depth data. The main etching step processing process can be pre-tested to detect the depth of sidewall distortion and record data, and it is preferable to select the time point for switching the different etching steps during the formal etching.

In the first embodiment of the present invention, the first etching gas selected by the etching gas introduced in the intermediate processing step has a high selection ratio of cerium oxide to tantalum nitride etching speed, for example, greater than 5, and the optimum requirement is greater than 8 That is, the rate of etching yttrium oxide is more than 8 times that of etched tantalum nitride. Exemplary, such as C4F6 (30sccm), C4F8 (30sccm), also need to pass other auxiliary gases such as Ar (100sccm) and O2 (45sccm), this intermediate treatment gas only etches yttrium oxide very fast, nitriding矽 can not be quickly etched. The first etching gas may also be other fluorocarbon gases such as C4F6, C3F8, C5F8, etc., all of which can achieve rapid etching of the yttrium oxide material layer while having a high selectivity ratio with respect to tantalum nitride. The main processing gas is mainly different from the main etching gas in the first step in that the second etching gas mainly used for the tantalum nitride is typically reduced, such as CH2F2, and other hydrocarbon compounds such as CHF and CH3F. Both can achieve the object of the present invention. Taking FIG. 1A as an example, when the sidewall of the etching hole is initially inclined, the bottom of the via hole is located on the yttrium oxide material layer 101 (SiO2), and at this time, since the sidewall region above the bottom of the via hole 102 has been formed by the pre-etching process. Complete protection, so only the bottom will still be etched. The first etching gas in the intermediate processing gas rapidly etches the yttrium oxide material layer 101, and since the polymer generated by the second etching gas is reduced, the via sidewall protective layer formed by the new etching at the bottom is weaker than the upper sidewall, so The isotropic etching is more obvious, and the left side inclined sidewall etching region has a larger surface area than the right vertical sidewall etching region, so the sloped portion at the bottom of the left side wall of the drawing is shrunk to the left side, and the right side is only a small amount of lateral etching, which finally makes The twisted portion of the entire through hole will be corrected. Since the sidewall morphology is corrected, the charge distribution accumulated in the sidewalls can also be partially improved, which is advantageous for maintaining the directivity of the etch through-holes 102 extending vertically downward in the next etching.

When the intermediate processing step continues to etch down so that the via 102 extends to the material layer of the tantalum nitride 103, the reaction rate of the downward etching is significantly lowered due to the high selectivity of the intermediate processing gas. The effect of the downward etching in the 103 material layer is mainly composed of the downwardly bombarded charged particles and the low-speed etching of part of the first etching gas, so the isotropic etching is no longer obvious, and the upper yttrium oxide material layer 101 is corrected. On the rear side wall, the topography of the through hole 102 is not excessively etched in the direction of the side wall by being deteriorated again. Eventually, the vertical sidewalls as shown in Figure 3 will be obtained when the intermediate processing steps are completed.

The intermediate processing step execution time can be preferably selected according to needs, and the correction of the sidewall through-hole morphology can be completed within a short period of time, such as 10 to 40 seconds, preferably within 30 seconds. After completing the intermediate processing step, the main etching step is again entered, and the main etching gas is re-introduced to continue the rapid etching down until the target depth is reached. If the depth required to be etched during the main etching step is still greater than 1.5 to 2 um, the intermediate processing step and the subsequent main etching step defined by the present invention are again performed until the target depth is reached.

In the present invention, when the main etching step is stopped, most of the sidewalls of only one layer of material start to be inclined, but in a small part, the inclined sidewalls appear continuously in the upper and lower material layers 101 and 103 of the through hole. For details, please refer to the structure. Figure 2A. To solve this problem, the present invention proposes a second embodiment in which the inclined portion on the sidewall of the upper layer of the cerium oxide material layer 101 is first etched away by the first etching gas after entering the intermediate processing step, exposing the layer 101 originally covered with the yttrium oxide material. The inclined portion in the layer of the tantalum nitride material 103 under the inclined portion, a partial enlarged view of the bottom structure of the through hole is as shown in FIG. 2B, and a stepped convex portion and a convex portion appear on the left side of the bottom of the through hole. Connected slopes. At this time, the main reaction gas in the intermediate process gas, that is, the first etching gas, cannot effectively etch the lower layer of tantalum nitride material 103, and the downward etching mainly relies on the downward bombardment of the charged particles. Since the stepped convex portion becomes a concentrated area of the electric boundary, similar to the tip discharge phenomenon, the incident charged particles will concentrate on the tip region to perform physical bombardment, and the inclined portion and the convex portion on the side wall can be etched after a certain period of etching. Etched, but the time taken is longer than in the first embodiment. Of course, after the etching of the inclined portion of the sidewall of the upper yttrium oxide material layer 101 is completed, when the sidewall of the tantalum nitride material layer 103 is etched, the first etching gas in the intermediate processing gas is replaced with the second etching gas. At this time, the principle of action is the same as that of the inclined portion of the sidewall of the ruthenium oxide material layer 101 in the first embodiment described above, but the reaction speed is relatively fast. Similarly, after completing the above intermediate processing steps, return to the main etching step and continue etching down until the target depth is reached. Or, in the intermediate processing step, the second etching gas is separately introduced, and after the etching for a certain period of time, the first etching gas is switched to be separately switched, except that the order of etching the material layers is different, and the sidewall shape on the two material layers can be corrected. The appearance of the present invention can also be achieved by distorting the appearance.

The intermediate processing gas in the intermediate processing step of the present invention may include a small amount of the second etching gas or other etching gas in addition to the first etching gas, but the selection of the intermediate processing gas component requires the first etching gas to etch the first material. The layer and the second material layer have a sufficient selection ratio, and the selection ratio is at least greater than 5, and the optimum requirement is greater than 8. Of course, it is also possible to pass only the second etching gas during the intermediate processing, and at the same time, the first etching gas is not introduced or introduced, so that the object of the invention can also be achieved, and the correction of the shape of the etched via hole can be realized. In the present invention, the intermediate processing step is added to the conventional processing step by less than 40 seconds, typically less than 30 seconds, and the overall main etching step is usually more than 200 seconds, and most processes require more than 300 seconds. Therefore, the time taken for the intermediate processing step is short compared to the duration of the entire etching step of 300 seconds or more, but the effect of the shape improvement is obvious, and no additional gas and other hardware changes are required, so It is possible to significantly improve the etching quality with a small increase in cost.

Since the first etching gas and the second etching gas selected by the prior art in the etching are all gas-rich components, it is easy to form a polymer protective layer on the sidewall, but the polymer protective layer will be etched. As the through hole is deeper and downward, it will accumulate more and more thickly, which will cause the diameter of the through hole to gradually decrease accordingly. The through hole formed by the etching will also become an inverted trapezoid which is large and small, which causes the performance of the semiconductor device. Negative Effects. In the present invention, a slight lateral etching of the bottom sidewall is realized by adding an intermediate processing step, in addition to the effect of the above-mentioned correction through the sidewall tilting, the diameter of the bottom of the large through hole can be simultaneously included to offset the adverse effect caused by the thickening of the polymer layer. Further improve the shape of the through hole.

The etching method proposed by the present invention includes a main etching step of etching a first material layer and a second material layer which are alternately stacked by introducing a main etching gas containing a first etching gas and a second etching gas in a main etching step. When the depth of the through hole formed by the etching reaches a certain value (1.5~2um), the process proceeds to the intermediate processing step, and in the intermediate processing step, the first etching gas is selected as the intermediate processing gas for etching, and the intermediate processing step is performed for a certain time to tilt the bottom side wall of the through hole. The portion is eliminated, wherein a first etching gas etches the first material layer and the second material layer has a selection ratio greater than 5, and the second etching gas etches the second material layer and the first material layer has a selection ratio greater than 5, preferably the above The choice ratio is greater than 8.

Although the present invention has been disclosed above, the present invention is not limited thereto. Any changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be determined by the scope defined by the appended claims.

100‧‧‧Substrate
101‧‧‧ layer of yttrium oxide material
102‧‧‧through hole
103‧‧‧layer of tantalum nitride material
105‧‧‧Material layer

1A and 1B are schematic views showing a process of forming a twisted through hole in an etching process by a multilayer material layer which is alternately laminated by a conventional technique;

2A is a schematic view showing the change of the sidewall shape of the through hole in the etching process of the second embodiment of the present invention, wherein FIG. 2B is a partially enlarged schematic view of the bottom of the through hole;

Figure 3 is a schematic illustration of the sidewall morphology of the via after completion of the intermediate processing steps of the present invention.

100‧‧‧Substrate

101‧‧‧ layer of yttrium oxide material

102‧‧‧through hole

103‧‧‧layer of tantalum nitride material

105‧‧‧Material layer

Claims (10)

A method for etching a multi-layer material layer by using a plasma, the multi-layer material layer comprising a plurality of layers of a first material layer and a second material layer alternately stacked, the etching method comprising: placing a substrate to be etched to a reaction a cavity, the upper layer of the substrate comprises the multi-layer material layer, the multi-layer material layer comprises a mask layer having an etched pattern thereon; performing a main etching step while introducing a first etching gas and a second etching gas to the Etching the multi-layer material layer in the reaction chamber until a through hole formed by etching reaches a first depth D, and switching to an intermediate processing step; performing the intermediate processing step, introducing the first etching gas or the second etching gas An etching gas is etched into the reaction chamber to correct the bottom layer topography, and the main etching step is performed again after the bottom surface topography is corrected; wherein the first etching gas is a material layer and the second material layer have an etching selectivity ratio greater than 5, and the second etching gas has a larger etching selectivity ratio to the second material layer and the first material layer 5. The etching method of claim 1, wherein the first etching gas has an etching selectivity ratio of the first material layer and the second material layer to be greater than 8. The etching method of claim 1, wherein the first material layer is a cerium oxide material layer, and the second material layer is a cerium nitride material layer, the first etching gas system comprising a fluorocarbon compound, The second etch gas system comprises a fluorohydrocarbon. The etching method according to claim 3, wherein the fluorocarbon compound comprises C4F8 and C4F6, and the fluorocarbon compound comprises CH2F2. The etching method of claim 1, wherein the multilayer material layer comprises the first material layer and the second material layer having a layer number greater than 24 layers, the multilayer material layer having a thickness greater than 2.4 microns. The etching method of claim 1, wherein the first depth D is less than 2 microns. The etching method of claim 6, wherein the first depth D is greater than 1.5 microns and less than 2 microns. The etching method of claim 7, wherein the main etching step is performed again such that the through hole depth extends downward a second time to a depth of 2D, and the intermediate processing step is performed again. The etching method of claim 1, wherein the intermediate processing step has a time of less than 40 seconds, and the length of the main etching step performed multiple times is greater than 200 seconds. A method for etching a multi-layer material layer by using a plasma, the multi-layer material layer comprising a plurality of layers of a first material layer and a second material layer alternately stacked, the etching method comprising: placing a substrate to be etched into a reaction chamber The substrate comprises a layer of the multi-layer material, the layer of the multi-layer material comprising a mask layer having an etched pattern thereon; performing a main etching step while introducing a first etching gas and a second etching gas to the reaction Etching the multi-layer material layer in the cavity until the through hole formed by the etching reaches a first depth D, and switching into an intermediate processing step; performing the intermediate processing step, introducing the first etching gas into the reaction chamber, and completing After the partial topography of the bottom of the through hole is corrected, the first etching gas is stopped, and the second etching gas is introduced into the reaction chamber, and the main etching step is performed again after the bottom surface topography is corrected; Wherein the first etching gas has an etching selectivity ratio to the first material layer and the second material layer greater than 5, the second etching gas is opposite to the second material layer and the second etching layer Etching selectivity ratio based material layer is greater than 5.