CN110896035A - Etching method - Google Patents
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- CN110896035A CN110896035A CN201811062202.3A CN201811062202A CN110896035A CN 110896035 A CN110896035 A CN 110896035A CN 201811062202 A CN201811062202 A CN 201811062202A CN 110896035 A CN110896035 A CN 110896035A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
- H01L21/4814—Conductive parts
- H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
- H01L21/4814—Conductive parts
- H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
- H01L21/4864—Cleaning, e.g. removing of solder
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Abstract
The invention provides an etching method, which comprises the following steps: forming an anti-reflection layer, a dielectric layer, a hard mask layer and a patterned photoresist layer on the metal conductor in sequence; etching the hard mask layer and the dielectric layer downwards along the patterned photoresist layer, and enabling a first etched side wall of the hard mask layer and a second etched side wall of the dielectric layer to form a smooth and continuous slope surface; and etching the anti-reflection layer and over-etching to the metal conductor. The invention provides a method for discharging metal byproducts generated by etching in the etching process, which improves the etching appearance of a metal channel, so that the filled metal conductor can be tightly attached to the side wall of the channel when the metal conductor is filled in the channel subsequently, and the problems of resistance value deviation of the metal channel, peeling of the metal filler and the like are solved.
Description
Technical Field
The invention relates to the field of integrated circuit manufacturing, in particular to an etching method.
Background
Metal conductive vias are currently used for internal circuit connections in integrated circuit fabrication. In order to connect the metal wires, a channel is etched, and a metal conductor is filled in the etched channel, so that the circuit connection effect is achieved.
Laser repair processes are currently used in the repair of circuits in integrated circuit manufacturing. The Laser repair process uses a Laser fuse in the Laser cutting circuit to change the decoding circuit, so that the defective memory cell is replaced by the backup circuit. The laser repair process can be divided into a welding area and a fuse area, wherein the welding area also needs to be etched with a metal channel, and the channel obtained by etching is filled with a metal conductor to finally form a welding pad.
However, in the above two processes, the resistance of the filled conductor is easily shifted and the metal filler is easily peeled off. These conditions severely affect the quality of the metal wire path and the bonding area. In view of the above, there is a need to improve the process of metal via design in order to improve the metal filling quality.
Disclosure of Invention
In view of the above-mentioned prior art, an object of the present invention is to provide an etching method for solving the problems of the prior art, such as the resistance value deviation of the conductor of the metal via and the peeling of the metal filler.
To achieve the above and other related objects, the present invention provides an etching method, comprising:
forming an anti-reflection layer, a dielectric layer, a hard mask layer and a patterned photoresist layer on the metal conductor in sequence;
etching the hard mask layer and the dielectric layer downwards along the patterned photoresist layer, and enabling a first etched side wall of the hard mask layer and a second etched side wall of the dielectric layer to form a smooth and continuous slope surface; and
and etching the anti-reflection layer and over-etching the anti-reflection layer until the metal conductor is obtained.
Optionally, the slope surface is discontinuous with an etching surface formed by etching the anti-reflection layer and over-etching the anti-reflection layer to the metal conductor.
Optionally, etching the hard mask layer, the dielectric layer, the anti-reflection layer and over-etching the metal conductor are continuously completed in a plasma etching reaction cavity.
Optionally, when the metal conductor is over-etched, introducing a protective gas to discharge a metal byproduct generated by etching the metal layer. The protective gas, which is a gas that does not react with the metal conductor during the immediate etching process, may be N2And inert gases such as Ar, He and Ne.
Further optionally, when the metal conductor is over-etched, the protective gas adopts N2CHF is adopted as the reaction gas3、CF4And O2Wherein CHF3The flow rate of (1) is 180-4The flow rate of (1) is 200-2The flow rate of (2) is 30-80sccm, N2The flow rate of (A) is 50-150 sccm.
Further optionally, when the metal conductor is over-etched, the protective gas adopts N2CHF is adopted as the reaction gas3、CF4And O2Wherein CHF3The flow rate of (1) is 180-4The flow rate of (1) is 200-2The flow rate of (2) is 30-80sccm, N2The flow rate of (1) is 200-600 sccm.
Optionally, before the hard mask layer and the dielectric layer are etched, a gas containing HBr is used for carrying out plasma treatment on the photoresist layer, and the side wall gradient of the photoresist layer is increased.
Further alternatively, HBr and N are used2The output power of the main radio frequency source is 200-2The flow rate of (A) is 50-150 sccm.
Optionally, when the metal conductor is over-etched, the output power of the bias rf source is 500-.
Optionally, when the metal conductor is over-etched, the output of the bias radio frequency source adopts a pulse mode, so that the bias radio frequency source is periodically turned on and off.
Further optionally, the bias rf source is turned on for a period of time within one duty cycle that is 20% to 50% of the total duration of the duty cycle.
Optionally, when the metal conductor is over-etched, the heating temperature is 40-60 ℃.
Optionally, after the hard mask layer and the dielectric layer are etched, O-containing is adopted2The etching of the hard mask layer and the side wall formed by the medium layer are subjected to plasma treatment by the gas, and the surface of the side wall is cleaned.
Further optionally, Ar and O are used2The mixed gas is used for carrying out plasma treatment on the side wall formed by etching the hard mask layer and the dielectric layer, the output power of a main radio frequency source is 200-800W, the frequency is 13MHz, the gas pressure is 40-100mTorr,the heating temperature is 40-60 ℃, and the total gas flow of the introduced gas is 100-600 sccm.
As described above, the etching method of the present invention has the following beneficial effects:
according to the invention, smooth and continuous slope surfaces are formed on the hard mask layer and the dielectric layer, so that the etching morphology of the metal channel is improved, the filled metal conductor can be tightly attached to the side wall of the channel when the metal conductor is filled in the channel subsequently, and the problems of resistance value deviation of the metal channel, peeling of the metal filler and the like are solved.
The invention also provides a method for discharging the metal by-product generated by etching in the etching process. By carrying out plasma treatment on the photoresist layer, the side wall gradient of the photoresist layer is increased, and a discharge channel of metal byproducts at the concave part in etching is widened under the condition of not influencing the structure of a device. By using a gas containing O2The etching side wall is subjected to plasma cleaning treatment by the gas, and the adhesive force of the treated etching side wall to the metal by-product is greatly reduced. And then, when the metal conductor is over-etched, adjusting etching parameters, including increasing airflow, introducing protective gas, increasing heating temperature, and adjusting the power or working mode of the bias radio frequency source, so that metal byproducts can be discharged more timely and fully in the etching process.
The metal by-product is discharged in the etching process, so that the metal by-product can be prevented from being attached to the etching surface in the etching process, and the etching appearance is improved. The obtained etched surface is smooth and has no sharp pricks, thereby being beneficial to the adhesion of a subsequent metal conductor and improving the quality of metal filling in an etched area.
Drawings
Fig. 1 shows a schematic flow chart of an etching method provided by the present invention.
FIG. 2 is a schematic diagram of defects caused by adhesion of metal byproducts generated during etching to the etched sidewalls.
Fig. 3a to 3d are schematic diagrams illustrating steps of the etching method according to the first embodiment of the invention, wherein fig. 3a is a schematic diagram illustrating the step S1, fig. 3b is a schematic diagram illustrating the step S2, fig. 3c is a schematic diagram illustrating the step S3, and fig. 3d is a schematic diagram illustrating a structure obtained after the step S3 is completed.
Fig. 4a to 4c are schematic diagrams illustrating steps of the etching method according to the third embodiment of the invention, wherein fig. 4a is a schematic diagram illustrating the step S1, fig. 4b is a schematic diagram illustrating the step S2, and fig. 4c is a schematic diagram illustrating the step S3.
FIG. 5a is a micro-topography of a photoresist layer before plasma treatment in accordance with a third embodiment of the present invention.
FIG. 5b is a micro-topography of the photoresist layer after plasma treatment in accordance with the third embodiment of the present invention.
FIG. 6a is a schematic diagram showing an etching process in a continuous mode for the output of the bias RF source.
Fig. 6b is a schematic diagram showing an etching process when the output of the bias rf source adopts a pulse mode according to the fifth embodiment of the present invention.
FIG. 6c is a schematic diagram showing the output of the bias RF source in a continuous mode.
Fig. 6d is a schematic diagram of the output of the five-bias rf source according to the embodiment of the present invention in the pulse mode.
Fig. 7a is a schematic diagram illustrating the step S2 executed in the seventh embodiment of the invention.
Fig. 7b is a schematic diagram illustrating the step S3 executed in the seventh embodiment of the invention.
FIG. 8a is a micro-topography of metal by-products from etching adhering to the etched sidewalls.
FIG. 8b is a micro-topography of the etched sidewall surface obtained by the etching method of the present invention.
Description of the element reference numerals
101 metallic conductor
102 dielectric layer
103 hard mask layer
104 photoresist layer
1021 antireflection layer
105 metal by-product
106 needle structure
107 fill conductor
a1 first etch sidewall
a2 second etching sidewall
a slope surface
b etching the anti-reflection layer and over-etching to the etched surface formed by the metal conductor
S1-S3 steps
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Referring to fig. 1, the present invention provides an etching method, including the following steps:
s1 forming an anti-reflection layer, a dielectric layer, a hard mask layer and a patterned photoresist layer on the metal conductor in sequence;
s2, etching the hard mask layer and the dielectric layer downwards along the patterned photoresist layer, and enabling the first etched side wall of the hard mask layer and the second etched side wall of the dielectric layer to form a smooth and continuous slope; and
s3 etching the anti-reflection layer and over-etching to the metal conductor.
The slope surface and an etching surface formed by etching the anti-reflection layer and over-etching the metal conductor are segmented and discontinuous.
According to the invention, smooth and continuous slope surfaces are formed on the hard mask layer and the dielectric layer, so that a channel with smooth side walls can be formed, and the etched channel can be used for filling a metal conductor. The invention improves the etching appearance of the metal channel, so that the metal conductor can be tightly attached to the side wall of the channel when the metal conductor is filled in the channel subsequently, and the problems of resistance value deviation of the metal channel filling conductor, peeling of the metal filler and the like are avoided.
The inventor researches to find that metal byproducts are generated in the etching process due to the need of over-etching to the metal conductor. As shown in fig. 2, metal byproducts 105 are generated when the anti-reflective layer 1021 is over-etched to the metal conductor 101, and the metal byproducts 105 adhere to the sidewall of the trench to form a micro hard mask, thereby resulting in the final appearance of the needle-like structure 106. In the subsequent step of filling the conductor 107, filling voids are generated due to the needle-like structures 106, which may cause a resistance shift in the electrical characteristics of the circuit. Moreover, these voids are also not favorable for adhesion between the filled conductor 107 and the trench sidewalls, and the metal filler is likely to peel off during the subsequent planarization step due to the reduced adhesion.
In order to form a smooth and continuous slope and improve the etching morphology, the metal by-product needs to be discharged in time during the etching process, so as to avoid or alleviate the defect caused by the adhesion of the metal by-product in the etching process. According to the invention, the side wall gradient of the photoresist layer is increased by carrying out plasma treatment on the photoresist layer; by using a gas containing O2The etching side wall is subjected to plasma cleaning treatment by the gas, so that the adhesive force of the metal by-product is greatly reduced; and adjusting the etching parameters when the metal conductor is over-etched, so that the metal by-product can be timely discharged in the etching process, and the etching appearance is improved.
The method of the present invention is further illustrated in detail below with reference to specific examples.
Example one
The embodiment provides an etching method, which includes the steps S1-S3. The following steps are specifically described with reference to fig. 3a to 3d as follows:
as shown in fig. 3a, a substrate to be etched is formed in step S1, and the substrate includes a metal conductor 101, a dielectric layer 102 to be etched, a hard mask layer 103, and a patterned photoresist layer 104. The dielectric layer 102 to be etched is located above the metal conductor 101, the hard mask layer 103 is located above the dielectric layer 102, and the photoresist layer 104 is located above the hard mask layer 103. The metal conductor 101 may be a metal wire layer including one or more layers of metal materials, or may be a functional layer containing metal materials for other purposes. The dielectric layer 102 to be etched may be an oxide layer as an insulating dielectric or other functional dielectric layer. An antireflection layer 1021 is also provided between the metal conductor 101 and the dielectric layer 102 to be etched.
As shown in fig. 3b, in step S2, the substrate to be etched may be placed in a plasma etching reaction chamber, the hard mask layer 103 and the dielectric layer 102 are etched downward by using the pattern of the photoresist layer 104, and the first etching sidewall a1 of the hard mask layer 103 and the second etching sidewall a2 of the dielectric layer 102 form a smooth and continuous slope surface a. Smooth and continuous slope surfaces are formed on the hard mask layer 103 and the dielectric layer 102, so that a channel with smooth side walls can be formed, and the etched channel can be used for filling a metal conductor. The etching of the hard mask layer 103, the dielectric layer 102 and the antireflection layer 1021 until the metal conductor 101 can be continuously completed in the plasma etching reaction chamber without multiple transfers. The basic structure and principle of the plasma etching reaction chamber are well known to those skilled in the art, and therefore, are not described herein.
As shown in fig. 3c, step S3 is continued to be performed in the plasma etching chamber, and the antireflection layer 1021 is etched and over-etched to the metal conductor 101, i.e. over-etched into the metal conductor 101, so as to ensure that no material of the antireflection layer 1021 remains.
In this embodiment, when the metal conductor 101 is over-etched, not only the reaction gas but also the protective gas is introduced. The metal by-product 105 generated by over-etching the metal conductor 101 is exhausted by using a protective gas. The protective gas is used in the etching processThe gas which does not react with the metal conductor 101 may be N2And inert gases such as Ar, He and Ne. The protective gas is introduced to increase the gas flow in the plasma etching reaction cavity in the etching process, so that the metal by-product 105 can be taken out, and the metal by-product 105 is difficult to accumulate on the etching surface under higher gas flow.
Specifically, when the metal conductor 101 is over-etched, the protective gas is N2CHF is adopted as the reaction gas3、CF4And O2Wherein N is2The flow rate of (1) is 50-150sccm, CHF3The flow rate of (1) is 180-4The flow rate of (1) is 200-2The flow rate is 30-80sccm, the gas pressure is 40-200mTorr, the output power of the main RF source is 500-1500W, the frequency is 60MHz, the output power of the bias RF source is 1000-2000W, the frequency is 13MHz, and the heating temperature is 30-45 ℃. Wherein, due to the addition of the protective gas, the O content can be properly reduced2The flow rate of (c).
The structure obtained after the etching is as shown in fig. 3d, smooth and continuous slope surfaces a are formed on the hard mask layer 103 and the dielectric layer 102, the antireflection layer 1021 is etched and over-etched until the etching surface b formed by etching the metal conductor 101 and the slope surfaces a formed by etching the hard mask layer 103 and the dielectric layer 102 are segmented and discontinuous, that is, they have different slopes.
Example two
This embodiment provides an etching method, which is substantially the same as the second embodiment except for the specific parameters in step S3. This embodiment increases N for faster and more timely venting of metal by-product 1052And adjusting the pressure in the reaction chamber, thereby further increasing the gas flow in the reaction chamber.
Specifically, when the metal conductor 101 is over-etched in step S3, the protective gas N is introduced2CHF, a reaction gas3、CF4And O2Wherein N is2The flow rate of (1) is 200-3The flow rate of (1) is 180-4The flow rate of the gas is 200-2The flow rate of the gas is 30-80sccm, and the gas pressure is 30-200mTorr, the output power of the main RF source is 500-1500W and the frequency is 60MHz, the output power of the bias RF source is 1000-2000W and the frequency is 13MHz, and the heating temperature is 30-45 ℃.
EXAMPLE III
In the present embodiment, an etching method is provided, which includes steps S1-S3, and the method performs a plasma treatment on the photoresist layer 104 before etching the hard mask layer 103 and the dielectric layer 102, so as to increase a sidewall slope of the photoresist layer 104, thereby facilitating the discharge of the metal byproduct 105 generated by over-etching. The following steps are specifically described with reference to fig. 4a to 4c as follows:
as shown in fig. 4a, a substrate to be etched is formed in step S1, and the substrate includes a metal conductor 101, a dielectric layer 102 to be etched, a hard mask layer 103, and a patterned photoresist layer 104. The dielectric layer 102 to be etched is located above the metal conductor 101, the hard mask layer 103 is located above the dielectric layer 102, and the photoresist layer 104 is located above the hard mask layer 103. An antireflection layer 1021 is also provided between the metal conductor 101 and the dielectric layer 102 to be etched. Then, the substrate to be etched is placed in a plasma etching reaction chamber, and plasma treatment is performed on the photoresist layer 104 to increase the sidewall gradient of the photoresist layer 104, so that the discharge channel of the metal by-product 105 in the pit during etching is widened without affecting the device structure.
In this example, HBr and N are used2The resist layer 104 is plasma-treated with the mixed gas. Specifically, the plasma etching reaction chamber may be evacuated, and then HBr and N may be introduced2Introducing HBr at a flow rate of 150-2The flow rate is 50-150sccm, the air pressure in the plasma etching reaction cavity is 30-100mTorr, the main radio frequency source of the plasma etching reaction cavity is started, the introduced gas is ionized, plasma is generated, the output power of the main radio frequency source is 200-800W, and the frequency is 60 MHz.
The photoresist layer 104 is modified by these plasmas to increase the sidewall slope of the photoresist layer 104. In this embodiment, the microstructure of the photoresist layer 104 before and after the plasma treatment is as shown in fig. 5a and 5b, the angle between the sidewall and the bottom of the photoresist layer 104 before the plasma treatment is 103.24 °, and the sidewall gradient is significantly increased when the angle is 148.53 ° after the plasma treatment.
Further, the substrate may be heated during the plasma treatment. Heating is typically carried out by an electrostatic chuck carrying the substrate at a temperature of 30-45 deg.c.
As shown in fig. 4b, step S2 is continuously performed in the plasma etching chamber, the hard mask layer 103 and the dielectric layer 102 are etched downward by using the pattern of the photoresist layer 104, and smooth and continuous slopes are formed on the hard mask layer 103 and the dielectric layer 102.
As shown in fig. 4c, step S3 is continued to be performed in the plasma etching chamber, and the antireflection layer 1021 is etched and over-etched to the metal conductor 101, i.e. over-etched into the metal conductor 101, so as to ensure that no material of the antireflection layer 1021 remains. The antireflection layer 1021 is etched and over-etched until the etched surface formed by the metal conductor 101 is discontinuous with the slope surface formed by etching the hard mask layer 103 and the dielectric layer 102. Since the sidewall slope of the photoresist layer 104 is increased, the metal by-products 105 generated by the over-etching are more easily exhausted.
Specifically, when the metal conductor 101 is over-etched, N is introduced2、CHF3、CF4And O2Gas, wherein N2The flow rate of (1) is 50-150sccm, CHF3The flow rate of (1) is 180-4The flow rate of (1) is 200-2The flow rate is 30-80sccm, the gas pressure is 40-200mTorr, the output power of the main RF source is 500-1500W, the frequency is 60MHz, the output power of the bias RF source is 1000-2000W, the frequency is 13MHz, and the heating temperature is 30-45 ℃.
Example four
The embodiment provides an etching method, which comprises steps S1-S3. This embodiment is substantially the same as the first embodiment, and the difference between the two embodiments is the specific process parameters in step S3. The present embodiment adjusts the output intensity of the biased rf source to vary the rate of reaction byproduct generation. When the rate of metal by-product 105 generation is reduced, it does not readily accumulate on the etch surface and is more easily exhausted during the etch process.
Specifically, in this embodiment, when the metal conductor 101 is over-etched in step S3, N is introduced2、CHF3、CF4And O2Gas, N2The flow rate of (1) is 50-150sccm, CHF3The flow rate of (1) is 180-4The flow rate of (1) is 200-2The flow rate is 30-80sccm, the gas pressure is 40-200mTorr, the output power of the main RF source is 500-1500W, the frequency is 60MHz, wherein the output power of the bias RF source is adjusted to 500-1800W, the frequency is 13MHz, and the heating temperature is 30-45 ℃.
EXAMPLE five
The present embodiment provides an etching method, which is substantially the same as the first embodiment except for the specific process parameters in step S3.
This embodiment also adjusts the output of the biased rf source to change the rate of reaction byproduct generation. In a conventional etch where the output of the bias rf source is continuous, i.e., in a continuous mode, the etch process is illustrated in fig. 6a, and metal by-products 105 are generated at the bottom of the trench and tend to accumulate on the sidewalls over time. Due to the continuous etching, the metal by-products 105 are continuously generated, and as the etching time increases, the metal by-products 105 are continuously accumulated. When a large amount of metal by-products 105 accumulate at the openings, reactants are not easy to enter the trenches, and the problem of reduced etching rate is also caused. In the present embodiment, the output of the bias rf source is changed to a pulse mode, so that the bias rf source is periodically turned on and off, as shown in fig. 6b, when the bias rf source is turned on, the reactant is etched to generate the metal byproduct 105, a small amount of the metal byproduct 105 is accumulated on the sidewall, and when the bias rf source is turned off, the metal byproduct 105 is not generated any more, so that the accumulated metal byproduct 105 is easily discharged. The bias rf source switch, the pulsed mode of the switch, thus facilitates the venting of the metal byproducts 105. Wherein the bias rf source continuous mode output is shown in fig. 6c, the bias rf source is continuously on during operation, and the bias rf source pulsed mode output is shown in fig. 6d, the bias rf source is periodically on and off during operation, each duty cycle comprising an on time and an off time.
Specifically, in this embodiment, when the metal conductor 101 is over-etched in step S3, CHF is introduced3、CF4And O2Gas, CHF3The flow rate of (1) is 180-4The flow rate of the gas is 200-2The flow rate is 100-. The heating temperature may be 20-45 ℃.
EXAMPLE six
The present embodiment provides an etching method, which is substantially the same as the first embodiment except for the specific process parameters in step S3. This embodiment increases the gas flow by warming, thereby making it easier to vent the metal by-product 105.
Specifically, in this embodiment, when the metal conductor 101 is over-etched in step S3, CHF is introduced3、CF4And O2Gas, CHF3The flow rate of (1) is 180-4The flow rate of the gas is 200-2The flow rate is 100-400sccm, the gas pressure is 40-200mTorr, the output power of the main RF source is 500-1500W, the frequency is 60MHz, the output power of the bias RF source is 1000-2000W, the frequency is 13MHz, wherein the heating temperature is 40-60 ℃, and the substrate can be heated by an electrostatic chuck.
EXAMPLE seven
The embodiment provides an etching method, which comprises steps S1-S3, and the method adopts O-containing after the hard mask layer 103 and the dielectric layer 102 are etched2The gas performs plasma treatment on the side wall formed by etching the hard mask layer 103 and the dielectric layer 102, and cleans the surface of the side wall, so that a metal byproduct generated by over-etching is difficult to attach. The following steps are specifically described with reference to fig. 7a and 7b as follows:
in step S1, the substrate provided in this embodiment includes a metal conductor 101, a dielectric layer 102 to be etched, a hard mask layer 103, and a patterned photoresist layer 104. The dielectric layer 102 to be etched is located above the metal conductor 101, the hard mask layer 103 is located above the dielectric layer 102, and the photoresist layer 104 is located above the hard mask layer 103. An antireflection layer 1021 is also provided between the metal conductor 101 and the dielectric layer 102 to be etched.
Step S2 is to place the substrate to be etched in a plasma etching reaction chamber, and etch the hard mask layer 103 and the dielectric layer 102 downward using the pattern of the photoresist layer 104 to form smooth and continuous slopes on the hard mask layer 103 and the dielectric layer 102. The substrate can be subjected to subsequent steps of plasma treatment and etching in the plasma etching reaction cavity without multiple transfers.
As shown in fig. 7a, the sidewalls formed by etching the hard mask layer 103 and the dielectric layer 102 are plasma-treated to clean the sidewall surface and reduce the adhesion of the sidewalls to the metal by-products. By using a gas containing O2The gas can remove the particle impurities remained on the etching medium layer 102, so that the surface of the side wall is cleaner and smoother. In this example, Ar and O are used2The mixed gas of (2) is subjected to plasma treatment. Specifically, the total gas flow of the introduced gas is 100-.
As shown in fig. 7b, step S3 is continued to be performed in the plasma etching chamber, and the antireflection layer 1021 is etched and over-etched to the metal conductor 101, i.e. over-etched into the metal conductor 101, so as to ensure that no material of the antireflection layer 1021 remains. The antireflection layer 1021 is etched and over-etched until the etched surface formed by the metal conductor 101 is discontinuous with the slope surface formed by etching the hard mask layer 103 and the dielectric layer 102. Since the adhesion to the metal by-product 105 is greatly reduced after the etching surface is cleaned, the metal by-product 105 is more easily discharged.
Specifically, when the metal conductor 101 is over-etched, CHF is introduced3、CF4And O2Gas, wherein CHF3The flow rate of (1) is 180-4The flow rate of (1) is 200-2The flow rate is 100-.
Fig. 8a is a microscopic topography of an etched sidewall surface after over-etching a metal conductor by a conventional etching method, wherein a smooth and continuous slope surface cannot be formed on the hard mask layer 103 and the dielectric layer 102 due to a rough etched surface and sharp spikes, which are caused by a metal byproduct generated by etching and adhered to the etched sidewall. FIG. 8b is a micro-topography of the etched sidewall surface obtained using the etching method of the example. It can be seen that the etched surface obtained by the etching method of the present invention is smooth, no needle-like structure occurs, the etching morphology is greatly improved, the first etched sidewall a1 of the hard mask layer 103 and the second etched sidewall a2 of the dielectric layer 102 form a smooth and continuous slope surface a, and the anti-reflection layer 1021 is etched and over-etched until the etched surface b formed by etching the metal conductor 101 and the slope surface a formed by etching the hard mask layer 103 and the dielectric layer 102 are segmented and discontinuous.
In summary, the invention improves the etching morphology of the metal channel by forming smooth and continuous slope surfaces on the hard mask layer and the dielectric layer, so that the filled metal conductor can be tightly attached to the side wall of the channel when the metal conductor is filled in the channel subsequently, and the problems of resistance value deviation of the metal channel, peeling of the metal filler and the like are solved. The invention also provides a method for discharging the metal by-product generated by etching in the etching process. By carrying out plasma treatment on the photoresist layer, the side wall gradient of the photoresist layer is increased, and a discharge channel of metal byproducts at the concave part in etching is widened under the condition of not influencing the structure of a device. By using a gas containing O2The etching side wall is subjected to plasma cleaning treatment by the gas, and the adhesive force of the treated etching side wall to the metal by-product is greatly reduced. Then, when the metal conductor is etched, the etching parameters including increasing airflow and passing are adjustedProtective gas is introduced, the heating temperature is increased, the power or the working mode of the bias radio frequency source is adjusted, and the metal by-products can be discharged more timely and fully in the etching process. The metal by-product is discharged in the etching process, so that the metal by-product can be prevented from being attached to the etching surface in the etching process, and the etching appearance is improved. The obtained etched surface is smooth and has no sharp pricks, thereby being beneficial to the adhesion of a subsequent metal conductor and improving the quality of metal filling in an etched area.
Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (14)
1. An etching method is characterized by comprising the following steps:
forming an anti-reflection layer, a dielectric layer, a hard mask layer and a patterned photoresist layer on the metal conductor in sequence;
etching the hard mask layer and the dielectric layer downwards along the patterned photoresist layer, and enabling a first etched side wall of the hard mask layer and a second etched side wall of the dielectric layer to form a smooth and continuous slope surface; and
and etching the anti-reflection layer and over-etching the anti-reflection layer until the metal conductor is obtained.
2. The etching method according to claim 1, characterized in that: the slope surface and an etching surface formed by etching the anti-reflection layer and over-etching the metal conductor are discontinuous in a segmented mode.
3. The etching method according to claim 1, characterized in that: and continuously finishing etching the hard mask layer, the dielectric layer, the antireflection layer and over-etching the metal conductor in a plasma etching reaction cavity.
4. The etching method according to claim 1, characterized in that: and when the metal conductor is over-etched, introducing protective gas to discharge a metal byproduct generated by etching the metal dielectric layer.
5. The etching method according to claim 4, wherein: when the metal conductor is over-etched, the protective gas adopts N2CHF is adopted as the reaction gas3、CF4And O2Wherein CHF3The flow rate of (1) is 180-4The flow rate of (1) is 200-2The flow rate of (2) is 30-80sccm, N2The flow rate of (A) is 50-150 sccm.
6. The etching method according to claim 4, wherein: when the metal conductor is over-etched, the protective gas adopts N2CHF is adopted as the reaction gas3、CF4And O2Wherein CHF3The flow rate of (1) is 180-4The flow rate of (1) is 200-2The flow rate of (2) is 30-80sccm, N2The flow rate of (1) is 200-600 sccm.
7. The etching method according to claim 1, characterized in that: and before the hard mask layer and the dielectric layer are etched, carrying out plasma treatment on the light resistance layer by using gas containing HBr, and increasing the side wall gradient of the light resistance layer.
8. The etching method according to claim 7, wherein: using HBr and N2The output power of the main radio frequency source is 200-2Flow rate of 50-150sccm。
9. The etching method according to claim 1, characterized in that: when the metal conductor is over-etched, the output power of the bias radio frequency source is 500-.
10. The etching method according to claim 1, characterized in that: and when the metal conductor is over-etched, the output of the bias radio frequency source adopts a pulse mode, so that the bias radio frequency source is periodically switched on and off.
11. The etching method according to claim 10, wherein: the bias RF source is turned on for a period of time that is 20-50% of the total duration of the duty cycle.
12. The etching method according to claim 1, characterized in that: and when the metal conductor is over-etched, heating to 40-60 ℃.
13. The etching method according to claim 1, characterized in that: after etching the hard mask layer and the dielectric layer, adopting O-containing2The etching of the hard mask layer and the side wall formed by the medium layer are subjected to plasma treatment by the gas, and the surface of the side wall is cleaned.
14. The etching method according to claim 13, wherein: with Ar and O2The mixed gas is used for carrying out plasma treatment on the side wall formed by etching the hard mask layer and the dielectric layer, the output power of the main radio frequency source is 200-800W, the frequency is 13MHz, the air pressure is 40-100mTorr, the heating temperature is 40-60 ℃, and the total flow of the introduced gas is 100-600 sccm.
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