TW201322328A - Etching method and etching device for mask layer and etching method for interlayer dielectric layer - Google Patents

Abstract

The invention discloses an etching method for a mask layer. The mask layer at least comprises a middle mask layer and an organic matter mask layer; the mask layer is etched with a plasma dry process; and in an etching process, a plasma radiofrequency excitation voltage is applied to generate plasma. The etching of the mask layer comprises the following steps of: forming a patterned middle mask layer by taking a patterned photoresist layer as a middle mask layer below mask etching; and applying a pulse bias radiofrequency voltage, and forming a patterned organic matter mask layer by taking the patterned middle mask layer as an organic matter mask layer below mask etching, wherein the frequency of the plasma radiofrequency excitation voltage is higher than that of the pulse bias radiofrequency voltage. The invention further provides an etching device for the mask layer and an etching method for an interlayer dielectric layer. Due to the adoption of the technical scheme provided by the invention, an implementation condition is simple and cost is low.

Description

Mask layer etching method, etching device and interlayer dielectric layer etching method

The present invention relates to the field of semiconductor manufacturing, and in particular to an etching method and an etching apparatus for a mask layer. Further, the present invention relates to an etching method of an interlayer dielectric layer.

In the semiconductor integrated circuit fabrication process, a semiconductor structure is formed on a semiconductor substrate by a series of processes such as deposition, photolithography, etching, planarization, and the like. Wherein, a photolithography process is used to form a mask pattern to define an area to be etched. The etching process is used to transfer the lithographically defined pattern onto the material (metal, dielectric layer or germanium) to form the desired structure. In the current semiconductor process, in order to enhance the transfer accuracy, lithography is generally defined. The pattern is transferred to the hard mask, and then the patterned hard mask is used as a mask to transfer the pattern to the material (metal, dielectric layer or germanium).

The transfer process of the above hard mask is usually performed by an etching process, and a plasma incident fit is required to control the etching direction and shape during the etching process. In the plasma etching process, a suitable gas is used as an etching gas, and an etching source is excited by an energy source such as a radio frequency source to form a plasma, and then etched by the plasma.

The etch rate and etch selectivity are two important indicators of plasma etch. The etching rate refers to the rate at which a certain material is etched per unit time by plasma etching; the etching selectivity ratio refers to the ratio of the etching rates of two different materials by plasma etching. Increasing the etch rate can increase the yield; increasing the etch selectivity can reduce other materials when etching the target material Loss. Therefore, in practical applications, it is desirable to have a high etching selectivity ratio at a high etching rate.

Different plasma incident energies affect the selection ratio of the material to be etched and the mask material. The larger the incident energy, the more obvious the physical bombardment phenomenon and the smaller the etching selectivity ratio. If the etching is mainly a chemical reaction, and the reaction gas has a large difference in the reaction speed of the two materials, the selection ratio is larger. In addition to the method of controlling the RF excitation source, the plasma incident energy can be controlled by changing the power of the RF bias source.

However, the inventors of the present invention have found that in the prior art, when etching a hole requiring a large aspect ratio (AR), for example, in a trench or connection hole process, the power of the RF and the bias RF is excited. In the hour, due to insufficient plasma incident energy, the protective film at the bottom of the opening cannot be blasted during the etching process under the opening, so that the reaction gas cannot continue to etch down, or cannot be etched down quickly, so the desired shape cannot be obtained. The etched pattern; when the power of the excited RF and the biased RF is too large, the incident of the plasma will cause damage to the mask layer, and as a result, the distortion of the mask pattern will be aggravated. Finding the right excitation RF and biasing RF power is difficult, time consuming and costly.

In view of this, it is necessary to propose a new etching method of the mask layer, which is simple in implementation and low in cost.

The problem solved by the present invention is to propose a new etching method of the mask layer to solve the problem of finding suitable excitation RF and bias RF power in the prior art, and obtaining the suitable excitation RF and bias RF is difficult and time consuming. Cost-consuming problem.

In order to solve the above problems, the present invention provides an etching of a mask layer. The mask layer includes at least an intermediate mask layer and an organic mask layer; the mask layer is plasma dry etched, and a plasma RF excitation voltage is applied during plasma dry etching to generate a plasma, wherein the mask layer The etching includes the steps of: etching the underlying intermediate mask layer with the patterned photoresist layer as a mask to form a patterned intermediate mask layer; applying a pulsed bias RF voltage and patterning the intermediate mask The layer is a mask to etch the underlying organic mask layer to form a patterned organic mask layer; wherein the frequency of the plasma RF excitation voltage is higher than the frequency of the pulsed bias RF voltage.

Optionally, the organic mask layer is amorphous carbon.

Optionally, the intermediate mask layer is a layer of inorganic material disposed under the photoresist layer.

Optionally, the layer of inorganic material is an inorganic anti-reflective layer.

Optionally, the thickness of the intermediate mask layer is less than the thickness of the organic mask layer.

Optionally, the frequency range of the pulsed biased RF voltage comprises: 2 MHz to 13 MHz.

Optionally, the frequency range of the plasma-excited RF voltage includes: 20 MHz to 120 MHz.

Optionally, the frequency of the pulsed biased RF voltage output is fixed or adjustable.

Alternatively, the plasma is an inductively coupled plasma or a capacitively coupled plasma.

In addition, the present invention also provides a mask etching apparatus, which is equipped with The apparatus includes a plasma reaction chamber in which a plasma generator for placing a substrate for processing a substrate and a plasma for generating a plasma in a space above the substrate in the reaction chamber is provided, and the base includes a lower electrode. A mask layer is disposed on the chip; wherein the lower electrode is connected to the RF bias power source; the RF bias power source is also connected to the RF bias power regulator, and the RF bias power regulator is used to adjust the output of the RF bias power pulse. Frequency; the plasma generator is connected to an RF excitation power supply.

Optionally, the plasma generator comprises an upper electrode and a coil, the upper electrode corresponding to the base and located at the top of the reaction chamber, the coil being located in the reaction chamber or a coil being located outside the reaction chamber.

The present invention also provides an etching method of an interlayer dielectric layer, comprising: providing a semiconductor substrate; sequentially forming an interlayer dielectric layer, an organic mask layer, and an intermediate mask layer on the semiconductor substrate; and applying photolithography on the intermediate mask layer Glue, transfer the mask pattern to the photoresist after exposure and development; plasma dry etching transfers the pattern on the photoresist to the intermediate mask layer, and then transfers the pattern on the intermediate mask layer to the organic material On the mask layer; a pulsed bias RF voltage is applied during the plasma dry etching; and the interlayer dielectric layer is etched by using the organic mask layer as a mask.

Optionally, the organic mask layer is made of amorphous carbon.

Optionally, the frequency range of the pulsed biased RF voltage comprises: 2 MHz to 13 MHz.

Optionally, the intermediate mask layer is an inorganic material layer, and the interlayer dielectric layer material is a cerium-containing inorganic material, wherein the intermediate mask layer has a thickness smaller than the thickness of the organic mask layer, and the organic mask layer has a thickness smaller than the interlayer dielectric layer thickness.

Compared with the prior art, the present invention has the following advantages: when transferring the pattern of the intermediate mask layer to the organic mask layer, the pulsed bias RF voltage is applied in a plasma dry etching process in one cycle. Internally, a part of the time period is biased with a radio frequency voltage to provide a biased RF power, which together with the excitation RF power provides the kinetic energy of the etching gas, so that when the plasma enters the organic mask layer, the kinetic energy is partially consumed, therefore, The problem of insufficient kinetic energy of the incident ions is avoided; the kinetic energy of the etching gas is only provided by the excitation RF power during the rest of the period, and the damage result caused by the continuous incidence of the plasma is suppressed; and the method is simple in implementation and low in cost.

Further, the intermediate mask layer is an inorganic anti-reflection layer disposed under the photoresist layer, and the etching ratio of the organic and inorganic materials in the organic mask layer disposed under the inorganic anti-reflection layer is increased, and the intermediate mask is improved. The transfer accuracy of the pattern of the film layer transferred to the organic mask layer.

Further, the frequency range of the pulsed bias RF voltage includes: 2MHz to 13MHz, and a suitable frequency pulse power source can be used according to the etching requirements of different materials to improve the transfer of the pattern of the intermediate mask layer to the organic mask layer. Transfer accuracy.

Further, the frequency of the pulsed bias RF voltage output is fixed or adjustable, and a fixed frequency is adopted, which can reduce the hardware cost achieved by the present invention, and adopts an adjustable frequency, similarly, according to the etching requirements of different materials. To achieve different etching effects.

As described in the background art, when etching some apertures requiring a large aspect ratio (AR), the power of the excitation RF and the bias RF is too small, the reaction gas cannot continue to etch down, or cannot be quickly turned Under etching, the etched pattern of the desired shape cannot be obtained; when the power of the excited RF and the biased RF is too large, the problem of eventually causing distortion of the mask pattern is aggravated.

The inventors of the present invention have analyzed this problem. In order to form a large aspect ratio hole, it is first necessary to obtain a stable final mask layer as a mask for downward etching, and the mask is generally obtained first. The lithography technique obtains a patterned photoresist, and then etches the intermediate mask layer (usually an inorganic material layer such as SiO2 or DARC material layer) with the photoresist, and finally etches the intermediate mask layer as a mask. The final mask layer below. The final mask layer can be amorphous carbon or a bottom layer photoresist layer (BPR) in a three-layer tri-layer. These materials generally have a thicker thickness generally greater than 50 nm, and even greater than 100 nm. The insulating material layer used for etching underneath, such as a Low-K material layer, typically has hundreds of nanometers (100-1000 nm, typically 500 nm), but Since these final mask layers are all organic, the organic matter is easily destroyed by incident high-energy plasma bombardment, and a chemical reaction-dominated etching process must be selected. However, when etching these materials, it is not possible to form a fluorocarbon-forming party by etching a fluorocarbon gas while etching a material such as low-K underneath, to protect the sidewalls, since etching organic materials is used. H2 is a reducing gas or an oxidizing gas such as O2 as a main etching gas, and is protected by a small amount of sidewall protective gas such as CO. So when etching this organic mask material It is difficult to form a very thick protective layer on the side walls and the top, and only a thin protective layer can be formed on the lower side walls. Therefore, there are many limitations in obtaining stable and reliable patterns when etching these materials.

In view of the above problems, the present invention proposes to apply a pulsed bias RF voltage in a plasma dry etching process when transferring the pattern of the intermediate mask layer to the organic mask layer, in a period, part of the time period The bias RF voltage is applied to provide the biased RF power, which together with the excitation RF power provides the kinetic energy of the etching gas, so that the kinetic energy is partially consumed when the plasma enters the organic mask layer, thereby avoiding the incident ion kinetic energy. Insufficient problem; the kinetic energy of the etching gas is only provided by the excitation RF power during the rest of the period, and the damage result caused by the continuous incidence of the plasma is suppressed; and the method is simple in implementation and low in cost.

The specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be noted that the following is a description of the principles of the invention and, therefore, is not to scale.

Embodiment 1

FIG. 1 is a flow chart of a method for etching a mask layer according to Embodiment 1, and FIG. 2 is a schematic diagram of a final structure after the method is completed. The method will be described in detail below with reference to FIGS. 1 and 2.

First, step S11 is performed to provide a semiconductor substrate. In the first embodiment, the semiconductor substrate is a germanium substrate 10, and germanium may be selected as needed.

Next, in step S12, a material layer, an organic mask layer, and an intermediate mask layer are sequentially formed on the germanium substrate 10.

The material layer may be a metal, a dielectric layer or a germanium. In the first embodiment, the interlayer dielectric layer 11 is taken as an example. The material of the interlayer dielectric layer 11 is a germanium-containing inorganic material, which may be used to form trenches in a subsequent process.

In the first embodiment, the organic mask layer is preferably an amorphous carbon layer 12, and a photoresist layer may be selected as needed, and the photoresist is disposed on the nitride or nitride-oxide-nitride as an intermediate mask layer. The bottom layer of the three-layer structure.

In the first embodiment, after the interlayer dielectric layer 11 is formed on the germanium substrate 10, the deposition of the intermediate mask layer is further performed in the first embodiment. The intermediate mask layer is an interlayer anti-reflection layer 13 (Darc), and the interlayer anti-reflection layer material may also be selected from other inorganic materials in the prior art, such as a nitride or nitride-oxide-nitride three-layer structure, or two. Yttrium oxide.

In view of the accuracy of subsequent pattern transfer, the thickness of the intermediate mask layer is preferably smaller than the thickness of the organic mask layer, and the thickness of the organic mask layer is preferably smaller than the thickness of the interlayer dielectric layer 11. In other embodiments, the intermediate mask layer may be selected from other inorganic material layers in addition to the interlayer dielectric layer 11.

Next, in step S13, the photoresist 14 is coated on the intermediate mask layer (the interlayer anti-reflective layer 13), and the mask pattern is transferred to the photoresist 14 after exposure and development. This step is a lithography process in the prior art, and details are not described herein again.

Next, in step S14, plasma dry etching transfers the pattern on the photoresist 14 to the intermediate mask layer (interlayer anti-reflection layer 13).

A plasma RF excitation voltage is applied during plasma dry etching of this step to generate a plasma, the RF excitation source typically having a higher frequency greater than 20 MHz, such as 27 MHz or 60 MHz, or even Above 100 MHz, for example 120 MHz, can be adjusted according to the plasma concentration and distribution requirements.

Then, in step S15, plasma dry etching transfers the pattern on the intermediate mask layer (interlayer anti-reflective layer 13) onto the organic mask layer.

In this step, in addition to applying the RF excitation voltage during the plasma dry etching process, a bias RF voltage is applied, and the bias RF voltage is pulsed. In this way, during a period of time, a part of the time period is biased with a radio frequency voltage to provide a biased RF power, which together with the excitation RF power provides the kinetic energy of the etching gas to avoid the kinetic energy portion when the plasma enters the organic mask layer. It is consumed, therefore, the problem of insufficient kinetic energy of the incident ions is avoided; the kinetic energy of the etching gas is only supplied by the excitation RF power during the rest of the period, and the damage caused by the continuous incidence of the plasma is suppressed. The power of the excitation RF and the bias RF is insufficient in the background art. Due to the insufficient incident energy of the plasma, the protective film at the bottom of the opening cannot be blasted during the etching process under the opening, so that the reaction gas cannot continue to etch down. Or, it is not possible to etch down quickly. Therefore, the etched pattern of the desired shape cannot be obtained. When the power of the excited RF and the biased RF is too large, the incident of the plasma will cause damage to the mask layer, and the result will be intensified. Film pattern distortion problem.

In a specific implementation process, since the plasma generated by the RF excitation voltage is mainly used for etching, the pulsed bias RF voltage serves as an auxiliary etching, and therefore, the frequency of the pulsed bias RF voltage is less than the RF excitation voltage. The frequency can range from 2MHz to 13MHz. It can be adjusted according to different materials and plasma input energy requirements. The lower the frequency, the greater the influence of plasma incident energy.

In addition, in the first embodiment, the pulse frequency of the pulsed bias RF voltage output is fixed. Taking a fixed frequency can reduce the hardware cost achieved by the present invention. In other embodiments, the pulse frequency can be set to be adjustable. With adjustable frequency, similarly, different etching effects can be achieved according to the etching requirements of different materials. The pulsed bias RF voltage refers to intermittently providing a RF bias voltage to the lower electrode. The RF bias voltage is applied to the lower electrode in a short time, and then the power supply is stopped until the next pulse period comes. Set the voltage. In this way, on the basis of not reducing the momentum of each incident ion, the time during which the mask is continuously bombarded is reduced, and the mask is effectively protected. The time during which the pulsed RF voltage is applied to the lower electrode accounts for less than 1/2 of the entire etching step, and even 1/4 can achieve good results. In the present invention, when the underlying organic material layer is etched by the intermediate mask layer, such etching is particularly effective, and the precise transfer of the pattern during the etching process can be ensured.

In a specific implementation process, the plasma generation may be an existing inductively coupled plasma or a capacitively coupled plasma. Therefore, the bias RF voltage of the present invention is pulsed and has good compatibility with existing processes.

At this point, the etching of the mask layer is completed. It can be seen that the mask layer referred to herein means an organic mask layer and an intermediate mask layer. In other embodiments, multiple layers of organic, inorganic alternating mask layers may also be employed to enhance the ultimate transfer accuracy.

Correspondingly, the device 2 for etching the mask layer in the first embodiment is implemented. As shown in FIG. 3, the device 2 includes: a plasma reaction chamber 21, and the plasma reaction chamber 21 is provided with a substrate for placing a substrate to be processed. a base plate and a plasma generator 23 for generating a plasma in a space above the substrate in the reaction chamber 21, The base includes a lower electrode 221, and a mask layer is disposed on the substrate; The lower electrode 221 is connected to the RF bias power supply 24; the RF bias power supply 24 is also connected to the RF bias power adjustment device 25, and the RF bias power adjustment device 25 is used to adjust the output frequency of the RF bias power supply 24 pulses. The plasma generator 23 is connected to an RF excitation power source 26.

In a specific implementation process, the plasma generator 23 includes an upper electrode 231 and a coil 232. The upper electrode 231 corresponds to the base and is located at the top of the reaction chamber 21, and a coil 232 is located outside the reaction chamber 21. In other embodiments, all of the coils may also be located within the reaction chamber 21.

During use, the plasma generator 23 is an inductively coupled plasma reactor or a capacitively coupled plasma reactor.

Embodiment 2

The second embodiment provides an etching method for the interlayer dielectric layer. As shown in FIG. 4, after the steps S11-S15 in the first embodiment are performed, step S16 is performed to mask the patterned organic mask layer. The film is etched under the interlayer dielectric layer 11. In the second embodiment, the organic mask layer follows the amorphous carbon layer 12 of the first embodiment.

The etching process in this step can be performed by plasma dry etching, and a plasma RF excitation voltage is applied to generate plasma in the process, and the frequency range of the plasma excitation RF voltage includes: 20 MHz to 120 MHz, depending on the plasma concentration and Distribution needs to adjust. In addition, this step can also use existing processes.

The above description is only a preferred embodiment of the invention and is not intended to limit the invention in any way. Anyone skilled in the art can use the present invention without departing from the scope of the technical solutions of the present invention. The method and the technical content disclosed above make many possible variations and modifications to the technical solutions of the present invention, or modifications to equivalent embodiments. Therefore, any simple modifications, equivalent changes, and modifications of the above embodiments may be made without departing from the spirit and scope of the invention.

10‧‧‧矽 substrate

11‧‧‧Interlayer dielectric layer

12‧‧‧Amorphous carbon layer

13‧‧‧Interlayer anti-reflection layer

14‧‧‧Photoresist

2‧‧‧ device

21‧‧‧Reaction chamber

221‧‧‧ lower electrode

23‧‧‧ Generator

231‧‧‧Upper electrode

232‧‧‧ coil

24‧‧‧RF bias power supply

25‧‧‧RF bias power regulator

26‧‧‧RF excitation power supply

1 is a flow chart of a method for etching a mask layer provided by one of the embodiments; FIG. 2 is a schematic diagram of a final structure after the method of FIG. 1 is completed; FIG. 3 is a schematic view of an etching device for a mask layer; 4 is a flow chart of an etching method of the interlayer dielectric layer provided in the second embodiment.

Claims (15)

An etching method for a mask layer, wherein the mask layer comprises at least an intermediate mask layer and an organic mask layer; the mask layer is etched by plasma dry etching, and the plasma dry etching process is applied The plasma RF excitation voltage is used to generate a plasma; the etching of the mask layer comprises the steps of: etching the underlying intermediate mask layer with the patterned photoresist layer as a mask to form a patterned intermediate mask layer; Pulse-biasing the RF voltage and etching the underlying organic mask layer with a patterned intermediate mask layer as a mask to form a patterned organic mask layer; wherein the frequency of the plasma RF excitation voltage is higher than the pulsed bias Set the frequency of the RF voltage. The method for etching a mask layer according to claim 1, wherein the organic mask layer is made of amorphous carbon. The method for etching a mask layer according to claim 1, wherein the intermediate mask layer is a layer of an inorganic material disposed under the photoresist layer. The method of etching a mask layer according to claim 3, wherein the inorganic material layer is an inorganic anti-reflection layer. The etching method of the mask layer according to claim 1, wherein the thickness of the intermediate mask layer is smaller than the thickness of the organic mask layer. The method for etching a mask layer according to claim 1, wherein the frequency range of the pulsed bias RF voltage comprises: 2 MHz to 13 MHz. The method for etching a mask layer according to claim 1, wherein the frequency range of the plasma excitation radio frequency voltage comprises: 20 MHz to 120 MHz. The etching method of the mask layer according to claim 1, wherein the frequency of the pulsed bias RF voltage output is fixed or adjustable. The method of etching a mask layer according to claim 1, wherein the plasma is an inductively coupled plasma or a capacitively coupled plasma. An etching device for a mask layer, wherein the device comprises: a plasma reaction chamber, wherein the plasma reaction chamber is provided with a base for placing the substrate to be processed and an upper space for the base in the reaction chamber a plasma plasma generator, the base comprising a lower electrode; wherein the lower electrode is connected to a radio frequency bias power supply; the radio frequency bias power supply is further connected to a radio frequency bias power supply adjusting device The output frequency of the RF bias power supply pulse is adjusted; the plasma generator is connected to the RF excitation power supply. An etch apparatus for a mask layer according to claim 10, wherein the plasma generator comprises an upper electrode and a coil, the upper electrode corresponding to the base and located at the top of the plasma reaction chamber, the coil being located in the reaction There is either a coil in the cavity outside the reaction chamber. An etching method of an interlayer dielectric layer, comprising: providing a semiconductor substrate; sequentially forming an interlayer dielectric layer, an organic mask layer, and an intermediate mask layer on the semiconductor substrate; and coating a photoresist on the intermediate mask layer, After the exposure and development, the mask pattern is transferred onto the photoresist; the plasma dry etching transfers the pattern on the photoresist to the intermediate mask layer, and then transfers the pattern on the intermediate mask layer to the organic mask. On the layer; the pattern on the intermediate mask layer is transferred during the plasma dry etching process A pulsed bias RF voltage is applied to the organic mask layer; the interlayer dielectric layer is etched using the organic mask layer as a mask. The method for etching an interlayer dielectric layer according to claim 12, wherein the organic mask layer is made of amorphous carbon. The method of etching an interlayer dielectric layer according to claim 12, wherein the frequency range of the pulsed bias RF voltage comprises: 2 MHz to 13 MHz. The method for etching an interlayer dielectric layer according to claim 12, wherein the intermediate mask layer is an inorganic material layer, and the interlayer dielectric layer is made of a germanium-containing inorganic material, wherein the intermediate mask layer has a thickness smaller than the The thickness of the organic mask layer, the thickness of the organic mask layer being less than the thickness of the interlayer dielectric layer.