Semiconductor line feature and manufacturing method thereof

Some embodiments of the present disclosure provide a semiconductor structure with a reduced line feature. The semiconductor structure includes a substrate, a first active region in the substrate and having a first sidewall, a second active region in the substrate and having a second sidewall, an isolation region contacting the first sidewall and the second sidewall. The above-mentioned semiconductor structure possesses a width of a top surface of the isolation region less than 50 nm and a width of a bottom surface of the isolation region more than 20 nm. Some embodiments provide a method for controlling a semiconductor line feature in a wafer, including patterning a hard mask exposing a line feature with a line width narrower than 50 nm on a wafer, forming a trench on the wafer correlated to the line feature by performing a plasma dry etch over the wafer, and filling the trench with isolation materials.

BACKGROUND

Shallow trench isolation (STI) is widely adopted in an integrated circuit (IC) to provide electrical isolation between adjacent semiconductor devices formed in a substrate. In a CMOS integrated circuit, STIs are typically formed between like kinds of NMOS or PMOS transistors in a given well or substrate to suppress leakage current between neighboring devices. These are generally referred to as intra-well isolations. STIs may also be formed between NMOS and PMOS transistors formed in separate wells. STIs thus formed are generally referred to as inter-well isolations and are typically used to suppress leakage current between neighboring devices of opposite-type and/or to prevent CMOS latchup from happening, which typically causes device failure.

STIs in a semiconductor device isolate a P-well and an N-well formed in a twin-well CMOS manufacturing process. NMOS and PMOS transistors are then formed in the P-well and N-well, respectively, having source/drain regions and gate regions. Inter-well STIs are formed to separate n+ region of NMOS transistor and p+ region of PMOS transistor. Intra-well STIs are also created to separate n+ region and an adjacent n+ region in the P-well, p+ region and an adjacent p+ region in the N-well, respectively.

STIs may start with forming an STI trench by an etching operation, overfilling the STI trenches with a dielectric such as an oxide, and then removing the dielectric outside the STI trenches. This dielectric helps to electrically isolate the active areas from each other. Typically, forming STI trenches involves creating shallow trenches into semiconductor substrate through an anisotropic etch operation, filling the STI trench with a dielectric material, such as CVD silicon oxide (SiO2), and removing the excess dielectric using a planarization process, such as chemical mechanic polishing (CMP). In general, the inter-well STI isolation spacing (i.e., n+-to-p+) is substantially wider than the minimum intra-well STI isolation spacing (i.e., n+-to-n+ or p+-to-p+) in order to provide desired isolation effects.

DETAILED DESCRIPTION

In the present disclosure, an “active region” performs the actual computing and storage operations of the semiconductor device. The active region in which amplifying, rectifying, or other dynamic action occurs in a semiconductor device. For example, the active region in the present disclosure refers to the transistor region where a gate, a source and a drain, and a semiconductor well are situated. The active region referred herein is not limited to a specific doping type but encompassing both the N-type transistor region and the P-type transistor region. The active region referred herein is not limited to a specific device geometry (e.g. planar transistor) but including both the planar MOSFET and the non-planar FinFET structure.

As the trend of integrating more and more circuit functions in a single IC continues, the structure of existing STIs is gradually becoming one of the major bottlenecks for the further device feature size scaling in advanced technology. Furthermore, a simple feature size shrinkage on an existing STI can lead to deteriorated isolation characteristics and poor device performance. For example, when the critical dimension of a CMOS structure scales down to below 40 nm, STIs prepared by conventional practice show a bridged bottom due to the fact that a tapered sidewall of the STI trench hinders the entrance of the etching gas and thus creates a spatial barrier for an effective etching. The bottom portion of the STI trench in a reduced dimension structure can be narrower than that in a wider dimension structure. Typically the bottom portion can be bridged by a deposition layer formed on sidewalls of the STI trench during an anisotropic dry etch. The formation of the deposition layer on the STI trench sidewalls can be referred to later description of the present disclosure.

One drawback or challenge related to the structure of a conventional STI in advanced processing technology is that a shrunken inter-well STI typically reduces the n+-to-N-well and p+-to-P-well spacing. This shrunken spacing is particularly severe in the bottom portion of the STI trench. When this spacing gets too small, the threshold voltage to turn on the channel regions of the parasitic field device along the side walls of an STI will become very low. Hence, leakage current may substantially increase along the P-well-to-STI, and N-well-to-STI interfaces.

Additional detrimental effects include lateral punch through in the parasitic device and latchup in the CMOS circuits. Although conventional remedies, such as an increased well dopant concentration and a precisely controlled well doping profile, may be employed to alleviate these problems, these remedies involve increased processing complexity and are generally very difficult to conduct in advanced technology.

Some embodiments of the present disclosure provide a reduced dimension STI structure which possesses an isolation region having a top surface width less than 50 nm and a bottom surface width more than 20 nm. In some embodiments, the reduced dimension STI structure provides two sidewalls of active regions adjacent to the isolation region to be more than 88 degrees.

Some embodiments of the present disclosure provide a method for manufacturing the reduced dimension STI structure described herein, and a method for controlling the line width feature of the reduced dimension STI structure on a wafer. In some embodiments, the manufacturing method provided herein includes temperature zone control of an electrostatic chuck (ESC) during etching operations and/or STI rounding operation. In some embodiments, the manufacturing method provided herein includes plasma density control across different zones during plasma etching operations.

FIG. 1shows a cross sectional view of a semiconductor structure10in accordance with some embodiments of the present disclosure. The semiconductor structure10includes a substrate100, a first active region101A and a second active region101B adjacent to the first active region101A, both positioned in the substrate100. The first active region101A refers to a particular area where the semiconductor device performs the actual computing and storage operations. For example, as shown inFIG. 1, the first active region101A includes a P-well102, an N-doped source region102sand an N-doped drain region102d, and an NMOS gate102g. Similarly, the second active region101B includes an N-well104, a P-doped source region104sand a P-doped drain region104d, and a PMOS gate104g. InFIG. 1, the P-well102of the first active region101A and the N-well104of the second active region101B are partially connected in proximity to a bottom portion of the two wells. However, an isolation region105is separating the P-well102of the first active region101A and the N-well104of the second active region101B, as well as the N-doped drain region102dand the P-doped source region104s. A first sidewall103A of the first active region101A and a second sidewall103B of the second active region101B are contacting the isolation region105.

The isolation region105has a top surface105twith a first width D1measured from a first boundary between the isolation region105and the first active region101A to a second boundary between the isolation region105and the second active region101B. In some embodiments, the first width D1of the top surface105tis less than 50 nm. Moreover, the isolation region105has a bottom surface105bwith a second width D2measured from a first boundary between the isolation region105and the first active region101A to a second boundary between the isolation region105and the second active region101B. In some embodiments, the second width D2of the bottom surface105bis more than 20 nm. In some embodiments, the isolation region is a shallow trench isolation (STI).

Still referring toFIG. 1, the first active region and the second active region described in the present disclosure are not limited to the active region with opposite doping type. In some embodiments, the third active region101D and the second active region101B possess same doping type. Isolation region107B separating the third active region101D and the second active region101B of the same doping type can be referred to as an intra-well isolation, whereas the isolation region107A separating the first active region101A and the second active region101B of different doping types can be referred to as an inter-well isolation. It shall be understood that the isolation structure described in the present disclosure encompasses both the inter-well isolation and the intra-well isolation. In some embodiments, the dimension of the intra-well isolation is smaller than the dimension of the inter-well isolation. However, all the isolation structures provided herein possess the first width D1of the top surface105tless than 50 nm and the second width D2of the bottom surface105bmore than 20 nm.

FIG. 2is an enlarged cross sectional view of the semiconductor isolation region105inFIG. 1in accordance with some embodiments of the present disclosure. An aspect ratio of the isolation region105can be defined as a ratio of a height H1of the isolation region105and an average of the first width D1and the second width D2(i.e., H1/(D1/2+D2/2)). In some embodiments, the aspect ratio of the isolation region105is within a range of from about 4 to about 10. InFIG. 2, the first sidewall103A possesses a sidewall angle θ1gripped between the first sidewall103A and a horizontal line extending into the first active region102. In some embodiments, the sidewall angle θ1is greater than 88 degrees. InFIG. 2, the second sidewall103B possesses a sidewall angle θ2gripped between the second sidewall103B and a horizontal line extending into the second active region104. In some embodiments, the sidewall angle θ2can be greater or smaller than 88 degrees. The first sidewall angle θ1can be equal to or different from the second sidewall angle θ2.

FIG. 3shows a cross sectional view of a plasma reactor used in some manufacturing methods provided in accordance with some embodiments of the present disclosure. A plasma reactor30for providing a high density plasma, on the order of about 1012ions per cm2, for etching a substrate, includes a plasma reactor chamber111that is fitted with a gas inlet114for receiving a processing gas into the chamber111. In addition to the gas inlet114, the chamber111is further provided with an outlet conduit (not shown) for connecting the chamber to an evacuation source, such as vacuum pump (not shown). The evacuation source should be sufficient to enable a very low operating pressure in the chamber in the range of about 1 to 50 mTorr, which is usually sufficient for maintenance of a high density plasma on the order of about 1012ions per cm2.

InFIG. 3, an ESC110supporting a wafer10′ including the semiconductor structure10as inFIG. 1is positioned close to a bottom portion of the chamber111. Two sets of electromagnetic coils are positioned above the chamber111. The first set of electromagnetic coils112A is situated close to a top middle portion of the chamber111, and the second set of electromagnetic coils112B is situated close to a top peripheral portion of the chamber111. According to the arrangement of the two sets of the electromagnetic coils, plasma density inside the chamber111can be separately controlled in two different zones. For example, the plasma density in zone I of the chamber111can be dominated by the current passing through the first electromagnetic coil112A, and zone I shown inFIG. 3refers to a center portion of the chamber111. On the other hand, the plasma density in zone II inside the chamber111can be dominated by the current passing through the second electromagnetic coil112B, and zone II shown inFIG. 3refers to a peripheral portion inside the chamber111.

As shown inFIG. 3, the first electromagnetic coil112A and the second electromagnetic coil112B are connected to a radio frequency (RF) signal source113through an impedance matchbox. In some embodiments, the radio frequency signal source113is capable of providing a radio frequency signal at about 13.56 MHz. In some embodiments, the ESC110may be configured to control the temperature of the wafer10′ by providing passages (not shown) in the ESC for flowing a fluid, such as water, or a gas, such as helium. In some embodiments, the ESC110may be configured to control the temperature of the wafer10′ by providing a higher amount of current passing through the conductive paths inside or around the ESC.

FIG. 4Ashows a top view of an ESC110with various temperature controlling zones supporting a wafer in accordance with some embodiments of the present disclosure. In some embodiments, two temperature zones, namely a higher temperature zone close to an edge of the wafer (1103,1104), and a lower temperature zone close to a center of the wafer (1101,1102) can be separately controlled by the means previously described in the present disclosure. In other embodiments, four temperature zones, namely the first zone1101, the second zone1102, the third zone1103, and the fourth zone1104, can be formed on the ESC110. However, the number of zones is not limited by the embodiments provided herein, any number of zones can be created as long as the equipment allows. As can be seen inFIG. 4A, a concentric-distributed temperature zones are provided. However, the geometry of the temperature distribution zones are not limited to the concentric fashion, other suitable temperature zone distribution are also applicable and shall be enclosed within the scope of the present disclosure.

FIG. 4Bshows a cross sectional view along line AA ofFIG. 4Ashowing the ESC110with various temperature zones in accordance with some embodiments of the present disclosure. InFIG. 4B, a wafer10′ is positioned on the ESC110with various temperature zones, and hence the wafer10′ can be subject to different temperature zones while the etching operation being performed thereon. For example, symmetric to the first temperature zone1101lies the second temperature zone1102, the third temperature zone1103, and the fourth temperature zone1104. Accordingly, the wafer10′ positioned on the ESC110can at least be divided into more than one temperature zones. In some embodiments, two temperature zones can be obtained by controlling the first temperature zone1101and the second temperature zone1102at one temperature, whereas controlling the third temperature zone1103and the forth temperature zone1104at another temperature. In some embodiments, four temperature zones can be achieved by separately controlling the four zones at different temperatures.

FIG. 5shows operations of the semiconductor isolation structure in accordance with some embodiments of the present disclosure. The operations includes patterning a hard mask exposing a line feature with a line width narrower than 50 nm on a wafer by performing a first plasma etch S501; forming a trench on the wafer correlated to the line feature by performing a second plasma etch over the wafer S502; and filling the trench with isolation materials S503. The first plasma etch further includes (1) forming at least two different temperature zones across the wafer, and (2) forming at least two different plasma density zones over the wafer.

FIG. 6toFIG. 11show cross sectional views of a semiconductor structure in various operational stages in accordance with some embodiments of the present disclosure. Operation S501is illustrated inFIGS. 6-8. InFIG. 6, a cross sectional view of a semiconductor structure under operation is shown. Numeral labels inFIG. 6that are identical to those inFIG. 1andFIG. 2refer to the same elements or their equivalents, hence is not repeated here for simplicity. The semiconductor structure inFIG. 6includes a first oxide layer601, a first hard mask layer603, and a second oxide layer605. A mask pattern layer including pattern features610,620,611,621are positioned on the second oxide layer605.

Referring toFIG. 6, in some embodiments, the pattern features610and611are identical, and the pattern features620and621are identical in terms of the multi-layer structure each possesses. For example, pattern features610and611have an ash-removable dielectric layer (ARD)602, a third oxide layer604, and a second hard mask layer606, whereas pattern features620and621have an ash-removable dielectric layer602and a third oxide layer60, but without the second hard mask layer606. The difference between the pattern features610and611and the pattern features620and621can be, for example, due to different manufacturing histories such that the pattern features610and611are defined in a different operation from the definition of the pattern features620and621. In some embodiments, defining the interlaced pattern features610,620,611,621in different operations is to achieve a smaller line width between adjacent pattern features.

Still referring toFIG. 6, the semiconductor structure is subject to two different zones A and B. In some embodiments, zones A and B are in contact with different temperature zones of an ESC. In some embodiments, zones A and B are situated in different plasma density zones. In the present disclosure, the different temperature zones can be roughly correlated to different plasma density zones. However, in some embodiments, the temperature zones may not be physically correlated to the plasma density zones. However, zone A shown inFIG. 6refers to a portion of the semiconductor structure close to a center of the wafer, whereas zone B refers to a portion of the semiconductor structure close to an edge of the wafer.

InFIG. 7, the first hard mask layer603is patterned by a first plasma etch to obtain a line feature D1′ which is narrower than 50 nm. In some embodiments, the first hard mask features610′,620′,611′,621′ are formed by an anisotropic plasma etch in a plasma etch chamber. The chamber pressure can be controlled within a range of from about 1 to about 10 mTorr with fluorine-containing etching gas70such as a mixture of CH2F2, CF4, O2, N2and Ar. During the plasma etch operation, the substrate is DC biased between about 100 volts and about 500 volts, while an RF discharge having a power between about 500 Watts and about 1000 Watts is released into the etch chamber. In alternative embodiments, an anisotropic reactive ion etch (RIE) may be used to remove the exposed portions of hard mask layer603, the first oxide layer601, and the second oxide layer605. Other suitable dry etch processes are not excluded from the scope of the present disclosure. In some embodiments, about 5% to about 10% over etch time is conducted in order to assure complete removal of hard mask layer603in the exposed areas.

In some embodiments, the etching of the first hard mask features610′ and621′ are subject to a first temperature imposed by specific temperature zones of the ESC inFIG. 4B. In the same operation, the etching of the first hard mask features620′ and611′ are subject to a temperature different from the first temperature imposed by another specific temperature zones of the ESC inFIG. 4B. In some embodiments, the first temperature imposed on the first hard mask features610′ and621′ forms a higher temperature zone close to an edge of the wafer, and another temperature zone imposed on the first hard mask features620′ and611′ forms a lower temperature zone close to a center of the wafer. In some embodiments, the higher temperature zone is maintained within a range of from about 40 to about 60 degrees Celsius. In some embodiments, the lower temperature zone is maintained three degrees lower than the corresponding higher temperature zone. As previously described, different temperature maintained at the higher temperature zone and the lower temperature zone can be controlled by flowing a fluid, such as water, or a gas, such as helium, to cool down the ESC, by passing desired amount of current into or around the ESC, or by the combination thereof.

Still referring toFIG. 7, during the patterning of the hard mask layer603, the current passing through the electromagnetic coils112A and112B may be different. In some embodiments, the current passing through the electromagnetic coil112B is greater than the current passing through the electromagnetic coil112A. Consequently, the plasma density formed in zone B (i.e., the region close to an edge of the wafer) can be either greater than or substantially equal to the plasma density formed in zone A (i.e., the region close to a center of the wafer). In some embodiments, a current ratio between the current entering the electromagnetic coil112A and112B is in a range of from about 0.5 to about 0.8. As shown inFIG. 7, the first hard mask features610′ and621′ are subject to a first plasma density zone established by the current passing through the electromagnetic coil112B, whereas the first hard mask features620′ and611′ are subject to a second plasma density zone established by the current passing through the electromagnetic coil112A. As can be seen inFIG. 7, the thickness of the ARD602varies between the first hard mask features610′,611′ and the first hard mask features620′,621′ due to the different masking patterns as illustrated inFIG. 6.

InFIG. 8, the ARD602is removed by an ash operation, and hence exposing the second oxide layer605underneath. Starting from this operation, the first hard mask features610′,620′,611′, and621′ are substantially identical masking patterns with a same multilayer structure.

Operation5502can be referred toFIGS. 9 and 10of the present disclosure. InFIG. 9, a second plasma etch is conducted to form trenches in the substrate100. In some embodiments, zones A and B are subject to a uniform second temperature imposed by the underneath ESC110shown inFIG. 4B. For example, the electrical current passing through different temperature zones of the ESC110is controlled in a specific amount to counter the fluid flowing through or around the ESC110in order to maintain a uniform and desired temperature across the ESC110. In some embodiments, the uniform second temperature is maintained in a range of from about 50 to about 80 degrees Celsius. In some embodiments, the second plasma etch operation is an in-situ, anisotropic plasma etch conducted in a same plasma etch chamber. This second plasma etch is a time-controlled process, and it continues until trenches with predetermined depth are created in semiconductor substrate100. The chamber pressure can be controlled within a range of from about 50 to about 100 mTorr with hydrogen halide etching gas90such as a mixture of HBr, O2, and N2. During the plasma etch operation, the substrate is DC biased between about 300 volts and about 1000 volts, while an RF discharge having a power between about 500 Watts and about 1000 Watts is released into the etch chamber. In alternative embodiments, an anisotropic reactive ion etch (RIE) may be used to remove the substrate100. Other suitable dry etch processes are not excluded from the scope of the present disclosure.

Referring toFIG. 9, O2/N2is used to react with etch byproducts SiBrxor SiOxNyto form and deposit SiBrxOy120on the trench sidewall. This deposit protects the sidewall and restricts the etch to the vertical direction, since SiBrxOy120deposited on the trench bottom105bis constantly removed by ion bombardment. The first hard mask patterns610′,620′,611′, and621′ are etched at a relatively slow rate compared to the substrate100, and in some embodiments, the taper-shaped first hard mask patterns610′,620′,611′, and621′ result to form an uneven trench bottom105bdue to the spatial hindrance of the ion bombardment. For example, the trench bottom105bincludes a subtrench105sclose to the corner of the trench bottom105band a convex portion105cclose to a center portion of the trench bottom105b. As shown inFIG. 9, a line width D1′ between two adjacent first hard mask patterns is narrower than 50 nm, while a width at trench bottom105bis more than 20 nm. In some embodiments, the uneven trench bottom105bis subsequently subject to a rounding operation as shown inFIG. 10to level the trench bottom105b.

Referring toFIG. 10, the rounding of the isolation trench bottom105bis conducted through a third plasma etch at the uniform second temperature. In some embodiments the temperature of the ESC110shown inFIG. 4Bis maintained at the second temperature during the trench formation and the rounding operation. The third plasma etch is an in-situ, anisotropic plasma etch conducted in a same plasma etch chamber. The chamber pressure can be controlled within a range of from about 1 to about 10 mTorr with hydrogen halide etching gas90′ such as a mixture of HBr, O2, and N2. During the third plasma etch operation, the substrate is DC biased between about 300 volts and about 1000 volts, while an RF discharge having a high power between about 1000 Watts and about 1500 Watts is released into the etch chamber. In alternative embodiments, an anisotropic reactive ion etch (RIE) may be used to remove the uneven trench bottom105b. Other suitable dry etch processes are not excluded from the scope of the present disclosure.

FollowingFIG. 10, the first hard mask pattern features610′,620′,611′, and621′ are removed by appropriate operations. A dielectric filling operation is subsequently performed to fill and overfill the isolation trench inFIG. 11. In some embodiments, silicon oxide is filled by a chemical vapor deposition CVD process. In some embodiments, a low pressure CVD (LPCVD) silicon oxide deposition, a high density plasma (HDP) silicon oxide deposition, a TEOS silicon oxide deposition, or an atmospheric pressure CVD (APCVD) silicon oxide deposition may also be used to fill the isolation trench. A planarization operation such as a chemical mechanical polishing (CMP) operation is performed to form a level surface which a top surface105tof the isolation region105is substantially coplanar with the substrate surface100t. The dimension of the isolation region105is detailed in the description referring to the semiconductor structure ofFIG. 1andFIG. 2.

Some embodiments of the present disclosure provide a semiconductor structure with a reduced line feature. The semiconductor structure includes a substrate, a first active region in the substrate and having a first sidewall, a second active region in the substrate, adjacent to the first active region, and having a second sidewall, an isolation region between the first active region and the second active region, contacting the first sidewall and the second sidewall. The above-mentioned semiconductor structure possesses a width of a top surface of the isolation region and a width of a bottom surface of the isolation region. The width of a top surface of the isolation region is less than 50 nm, and the width of a bottom surface of the isolation region is more than 20 nm.

In some embodiments of the present disclosure, the isolation region is shallow trench isolation (STI).

In some embodiments of the present disclosure, an aspect ratio of the isolation region is in a range of from about 4 to about 10.

In some embodiments of the present disclosure, the first sidewall of the first active region includes a sidewall angle greater than 88 degrees.

Some embodiments of the present disclosure provide a manufacturing method for a semiconductor isolation structure with reduced line features. The method includes patterning a hard mask exposing a line feature with a line width narrower than 50 nm on a substrate by performing a first plasma etch at a first temperature, forming a trench in the substrate correlated to the line feature by performing a second plasma etch at a second temperature, rounding the bottom of the trench by performing a third plasma etch at the second temperature, and filling the trench with isolation materials.

In some embodiments of the present disclosure, the patterning a hard mask includes controlling the amount of current passing through an electrostatic chuck (ESC) supporting the substrate to maintain the first temperature.

In some embodiments of the present disclosure, the first temperature is controlled to be within a range of from about 404 to about 60 degrees Celsius.

In some embodiments of the present disclosure, the forming a trench in the substrate and rounding the bottom of the trench includes controlling the amount of current passing through an ESC supporting the substrate to maintain the second temperature.

In some embodiments of the present disclosure, the second temperature is controlled to be within a range of from about 50 to about 80 degrees Celsius

In some embodiments of the present disclosure, the patterning a hard mask exposing a line feature includes introducing fluorine-containing gas, oxygen gas, and nitrogen gas into an etching chamber.

Some embodiments of the present disclosure provide a method for controlling a semiconductor line feature in a wafer. The method includes patterning a hard mask exposing a line feature with a line width narrower than 50 nm on a wafer by performing a first plasma etch, forming a trench on the wafer correlated to the line feature by performing a second plasma etch over the wafer, and filling the trench with isolation materials. The first plasma etch includes forming at least two different temperature zones across the wafer and forming at least two different plasma density zones over the wafer.

In some embodiments of the present disclosure, the forming at least two different temperature zones across the wafer includes forming concentric-distributed temperature zones with a higher temperature zone close to an edge of the wafer and a lower temperature zone close to a center of the wafer.

In some embodiments of the present disclosure, the forming concentric-distributed temperature zones include passing different amount of current through different temperature zones.

In some embodiments of the present disclosure, the forming at least two different plasma density zones over the wafer includes forming concentric-distributed plasma density zones with a higher plasma density close to an edge of the wafer and a lower plasma density close to a center of the wafer.

In some embodiments of the present disclosure, the forming at least two different plasma density zones over the wafer includes applying a current ratio between the current entering the magnetic coils close to the center of the wafer and the current entering the magnetic coils close to the edge of the wafer to be lower than 0.8.

In some embodiments of the present disclosure, the method for controlling a semiconductor line feature in a wafer further includes performing a rounding operation at the bottom of the trench under a uniform temperature across different temperature zones

In some embodiments of the present disclosure, the uniform temperature is in a range of from about 50 to about 80 degrees Celsius.

In some embodiments of the present disclosure, the higher temperature zone close to the edge of the wafer is three degrees greater than the lower temperature zone close to the center of the wafer.

In some embodiments of the present disclosure, the performing the first plasma etch over the wafer includes introducing fluorine-containing gas, oxygen gas, and nitrogen gas into an etching chamber.

In some embodiments of the present disclosure, the performing the second plasma etch over the wafer includes introducing hydrogen halide gas, oxygen gas, and nitrogen gas into an etching chamber.