Etching rate measuring method and wafer pre-cleaning process

Abstract

The invention provides an etching rate measuring method and a wafer pre-cleaning process, and the method comprises the following steps: providing a substrate, and forming a to-be-etched layer on the upper surface of the substrate; processing the to-be-etched layer on the upper surface of the substrate for a first preset time by using a first etching agent so as to reduce the thickness of the to-be-etched layer by a preset thickness; measuring the current value of the thickness of the to-be-etched layer treated by the first etching agent, and treating the to-be-etched layer on the upper surface of the substrate for a second preset time by adopting a second etching agent under the preset etching parameters; and measuring the final value of the thickness of the to-be-etched layer treated by the second etching agent, and calculating the etching rate of the second etching agent corresponding to the preset etching parameter. According to the invention, the etching rate measurement process is improved, and the first etching agent treatment is carried out for the first preset time before the second etching agent treatment is carried out, so that the etching rate measurement error is reduced, and the uniformity of the etching thickness of the wafer pre-cleaning process is improved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor integrated circuit manufacturing and relates to an etching rate measurement method and a wafer pre-cleaning process. Background Art

[0002] With the development of integrated circuits (ICs) from small scale, large scale to ultra-large scale, the density and integration of devices in integrated circuits have been continuously improved, making the size of devices continuously shrinking. However, the continuous reduction of device size has brought many difficulties to the manufacturing of devices. The introduction of plasma technology has solved many problems in the manufacturing process of devices.

[0003] Applying plasma technology to the pre-cleaning process before device metallization can remove pollutants and particles on the wafer surface, and can also remove the natural oxide layer produced on the wafer surface exposed at the bottom of the contact hole exposed to the air, so as to prevent the natural oxide layer on the wafer surface at the bottom of the contact hole from affecting the metal layer deposition, and at the same time, to form a better contact between the metal layer and the wafer. For the pre-cleaning process before device metallization, the rate of the etching gas is usually measured before the cleaning process is carried out, so as to set the cleaning time and ensure that the natural oxide layer at the bottom of the contact hole can be completely removed.

[0004] At present, the measurement of the etching rate of the pre-cleaning process is usually carried out by depositing a silicon oxide layer (formed by the reaction of deposited ethyl silicate with oxygen) on the surface of the wafer, measuring the thickness of the wafer after the silicon oxide layer is formed, and then performing plasma argon cleaning and etching for a set time (about etching time). ), and then measure the thickness of the wafer after etching to calculate the etching rate under the argon concentration, so as to set the etching time for subsequent pre-cleaning. However, the pre-cleaning time is set based on the etching rate measured by this method. Since the measured etching rate has a large error with the actual etching rate of the pre-cleaning process, the thickness uniformity of the wafer after the argon cleaning process and the uniformity of the average etching thickness between different batches of wafers are poor. Figure 1 As shown in the figure, it can be seen that the cleaning time is set based on the etching rate measured by this method. After the pre-cleaning process, the average etching thickness of different batches of wafers varies greatly, and the uniformity of the thickness of the wafers also fluctuates greatly, which is not conducive to the performance control of the manufactured devices.

[0005] Therefore, there is an urgent need to find an etching rate measurement method that can reduce the etching rate measurement error. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an etching rate measurement method and a wafer pre-cleaning process, which are used to solve the problem that the etching rate measurement error in the prior art affects the performance of the device after etching.

[0007] To achieve the above object and other related objects, the present invention provides an etching rate measurement method, comprising the following steps:

[0008] Providing a substrate, and forming a to-be-etched layer with a preset thickness on the upper surface of the substrate;

[0009] Treating the layer to be etched on the upper surface of the substrate with a first etchant for a first preset time to reduce the layer to be etched on the substrate to a preset thickness;

[0010] Measuring a current value of the thickness of the layer to be etched after being treated with the first etchant, and treating the layer to be etched on the upper surface of the substrate with a second etchant under preset etching parameters for a second preset time;

[0011] The final value of the layer to be etched after being treated with the second etchant is measured, and based on the difference in thickness of the layer to be etched before and after being treated with the second etchant, the etching rate of the second etchant under the preset etching parameters is calculated.

[0012] Optionally, before forming the layer to be etched, a step of measuring the thickness of the substrate is further included, and the thickness of the layer to be etched is the difference between the sum of the thicknesses of the substrate and the layer to be etched and the thickness of the substrate.

[0013] Optionally, the state of the first etchant includes one of a liquid state and a gaseous state; and the components of the second etchant include at least argon gas.

[0014] Optionally, the material of the layer to be etched includes silicon, silicon oxide, silicon nitride, or silicon oxynitride.

[0015] Optionally, the first etchant and the second etchant have the same component.

[0016] Optionally, the preset thickness range is

[0017] Optionally, the instrument for measuring the thickness of the layer to be etched includes a non-contact thickness gauge.

[0018] Optionally, after being treated with the second etchant, the thickness of the layer to be etched is reduced to a value in the range of

[0019] Optionally, after measuring the current value of the thickness of the layer to be etched after being treated with the first etchant, before using the second etchant to treat the layer to be etched for the second preset time, the step also includes placing the substrate treated with the first etchant in a process chamber of an etching machine.

[0020] The present invention also provides a wafer pre-cleaning process, wherein the pre-cleaning time of the wafer pre-cleaning process is set based on the etching rate measured by the etching rate measurement method described above.

[0021] As described above, the etching rate measurement method and wafer pre-cleaning process of the present invention improve the etching rate measurement method. After the layer to be etched of a preset thickness is formed on the upper surface of the substrate, before the current value of the thickness of the layer to be etched is measured, the first etchant is used for treatment for a first preset time to remove the portion of the upper surface layer of the layer to be etched with poor quality, thereby improving the uniformity of the quality of the layer to be etched. After the current value of the thickness of the layer to be etched is measured, the second etchant is used for treatment for a second preset time under the preset etching parameters, and the final value of the thickness of the layer to be etched after treatment with the second etchant is measured, and the etching rate of the second etchant under the preset etching parameters is calculated, thereby reducing the etching rate error of the second etchant corresponding to the measured preset etching parameters. In addition, the second etchant and the preset etching parameters are respectively used as the etchant and etching parameters of the wafer pre-cleaning process, and the etching rate of the second etchant measured under the preset etching parameters is used to set the cleaning time of the wafer pre-cleaning process, thereby improving the thickness uniformity of the wafer after pre-cleaning, and at the same time improving the uniformity of the average etching thickness between different batches of wafers after pre-cleaning, which has high industrial utilization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The graph shows the thickness uniformity of wafers from different batches after wafer pre-cleaning before metallization and the average etch thickness statistics between wafers from different batches.

[0023] Figure 2 Shown is a process flow chart of the etching rate measurement method of the present invention.

[0024] Figure 3 Shown is a statistical chart of thickness uniformity of wafers of different batches after pre-cleaning by the wafer pre-cleaning process of the present invention and average etching thickness between wafers of different batches. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0026] See also Figures 2 to 3 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0027] Embodiment 1

[0028] This embodiment provides an etching rate measurement method, such as Figure 2 As shown, it is a process flow chart of the etching rate measurement method, which includes the following steps:

[0029] S1: providing a substrate, and forming a layer to be etched with a preset thickness on the upper surface of the substrate;

[0030] S2: using a first etchant to treat the layer to be etched on the upper surface of the substrate for a first preset time, so as to reduce the layer to be etched on the substrate to a preset thickness;

[0031] S3: measuring a current value of the thickness of the layer to be etched after being treated with the first etchant, and treating the layer to be etched on the upper surface of the substrate with a second etchant under preset etching parameters for a second preset time;

[0032] S4: measuring a final value of the thickness of the layer to be etched after being treated with the second etchant, and calculating an etching rate of the second etchant corresponding to the preset etching parameters based on a difference in thickness of the layer to be etched before and after being treated with the second etchant.

[0033] Specifically, please perform the step S1 and the step S2: provide a substrate, and form a layer to be etched of a preset thickness on the upper surface of the substrate; use a first etchant to treat the layer to be etched on the upper surface of the substrate for a first preset time to thin the layer to be etched on the substrate to a preset thickness.

[0034] Specifically, the substrate is made of glass, wafer, sapphire or other suitable substrate materials. Preferably, a wafer is used as the substrate.

[0035] Specifically, under the condition of ensuring the film quality of the layer to be etched, the size, thickness and shape of the substrate 1 can be selected according to actual conditions and are not limited here.

[0036] As an example, a method of forming the layer to be etched includes chemical vapor deposition or other suitable methods.

[0037] Specifically, under the condition that the thickness of the layer to be etched is ensured to be sufficient to measure the etching rate of the second etchant, the thickness of the layer to be etched can be selected according to actual conditions, and is not limited here.

[0038] Specifically, since different etchants usually have different etching rates for different materials, in order to reduce the error of the etching rate and ensure the accuracy of the etching rate, the material of the layer to be etched is usually the same as the material of the film layer to be removed in the etching process and is a single film layer.

[0039] As an example, the material of the layer to be etched includes silicon, silicon oxide, silicon nitride, silicon oxynitride or other suitable materials. In this embodiment, a chemical vapor deposition method is used to introduce tetraethyl orthosilicate (TEOS) gas and oxygen into a deposition chamber at a certain temperature and pressure, and the tetraethyl orthosilicate gas and oxygen react on the upper surface of the substrate to form silicon oxide of a preset thickness.

[0040] Specifically, after the layer to be etched is formed, the method further includes taking out the substrate with the layer to be etched formed on its upper surface from the deposition chamber in which the layer to be etched is formed.

[0041] Specifically, the method of taking out the substrate having the layer to be etched formed on the upper surface thereof from the deposition chamber is a commonly used wafer taking out method, which will not be described in detail here.

[0042] Specifically, after forming the layer to be etched and before using the first etchant to process the layer to be etched on the upper surface of the substrate, the method also includes placing the substrate with the layer to be etched in a processing machine to facilitate processing of the layer to be etched on the upper surface of the substrate.

[0043] Specifically, the method of placing the substrate in the processing machine is a commonly used substrate placement method, which will not be described in detail here.

[0044] As an example, the state of the first etchant includes one of liquid and gaseous states, that is, the method of using the first etchant to process the layer to be etched can be wet etching or dry etching. Preferably, the state of the first etchant is gaseous, that is, dry etching is used to process the layer to be etched on the upper surface of the substrate for the first preset time.

[0045] Specifically, the value of the first preset time is related to the concentration of the first etchant, the processing ambient temperature and the material of the layer to be etched. While ensuring that the thinned thickness of the layer to be etched after processing is within the preset thickness range, the first preset time can be selected according to actual conditions and is no longer restricted here.

[0046] As an example, the range of the preset thickness is Preferably, the preset thickness is That is, through the treatment of the first etchant, the layer to be etched is thinned from the upper surface downward.

[0047] Specifically, in the process of using the first etchant to process the layer to be etched, in order to ensure the accuracy of subsequent measurements, it is necessary to ensure that the first etchant does not react with the bottom surface area of ​​the substrate. Therefore, when the substrate also reacts with the first etchant, it is necessary to adopt protective measures to avoid the reaction on the bottom surface of the substrate, for example, a protective film may be mounted.

[0048] Specifically, since the upper surface layer of the layer to be etched formed by the deposition process is usually a region of poor quality, the layer to be etched on the upper surface of the substrate is treated with the first etchant to remove the film layer region of poor quality on the upper surface of the layer to be etched, thereby improving the uniformity of the quality of the remaining film layer, and then ensuring the uniformity of the etching rate in the subsequent treatment process of the second etchant, thereby reducing the measurement error of the etching rate.

[0049] Specifically, please execute step S3 and step S4: measure the current value of the thickness of the layer to be etched after being treated with the first etchant, and use the second etchant to treat the layer to be etched on the upper surface of the substrate for a second preset time under preset etching parameters; measure the final value of the thickness of the layer to be etched after being treated with the second etchant, and calculate the etching rate of the second etchant corresponding to the preset etching parameters based on the difference in thickness of the layer to be etched before and after being treated with the second etchant.

[0050] As an example, the instrument for measuring the thickness of the layer to be etched includes a non-contact thickness gauge or other suitable instruments for measuring thickness. In this embodiment, the thickness gauge used is to measure the thickness of the layer to be etched using an optical measurement method. Since the optical measurement method can achieve non-contact measurement of thickness, the problem of contaminating the layer to be etched and the substrate caused by measuring the thickness of the layer to be etched is avoided, and the cleanliness of the surface of the layer to be etched and the substrate during the thickness measurement process is ensured.

[0051] Specifically, after the layer to be etched is treated with the first etchant, the thickness of the layer to be etched is measured to determine the thickness of the layer to be etched before being treated with the second etchant, so as to calculate the thickness of the layer to be etched that is reduced during the treatment with the second etchant.

[0052] As an example, before forming the layer to be etched, a step of measuring the thickness of the substrate is also included, and the thickness of the layer to be etched is the difference between the sum of the thicknesses of the substrate and the layer to be etched and the thickness of the substrate.

[0053] Specifically, when the thickness of the layer to be etched is not easy to measure and the first etchant and the second etchant have no effect on the substrate during the process of treating the layer to be etched, the thickness of the substrate can be measured before forming the layer to be etched, and then when the thickness of the layer to be etched needs to be measured, the thickness of the layer to be etched can be directly measured, and the thickness of the layer to be etched can be calculated by using the difference between the sum of the thicknesses of the substrate and the layer to be etched and the initial thickness of the substrate.

[0054] As an example, after measuring the thickness of the layer to be etched after being treated with the first etchant, before using the second etchant to treat the layer to be etched for the second preset time, the method also includes placing the substrate treated with the first etchant in a process chamber of an etching machine.

[0055] Specifically, the method of placing the substrate treated with the first etchant in the process chamber of the etching machine is a common placement method, which will not be described in detail here.

[0056] As an example, the second etchant includes at least argon gas. Preferably, argon gas is selected as the second etchant, and argon ions generated by argon gas are used to bombard the upper surface of the layer to be etched, so as to etch the layer to be etched.

[0057] Specifically, in the process of the second etchant treating the layer to be etched, except for the set etching time, other etching parameters are consistent with the parameters of the etching process to be performed, such as the power of the machine and the gas flow rate in dry etching.

[0058] Specifically, the preset etching parameters affect the etching machine parameters and etching environment parameters of the etching rate, such as the power of the etching machine, the flow rate of the etchant, the temperature of the etching process chamber, etc., which will not be described one by one here.

[0059] Specifically, the parameter values ​​of the preset etching parameters can be selected according to actual conditions and are not limited here.

[0060] As an example, the first etchant has the same composition as the second etchant.

[0061] Specifically, the first etchant and the second etchant may be completely the same, so as to avoid processing with multiple etchants and increasing the complexity of the measurement process.

[0062] Specifically, the processing parameters of the first etchant and the second etchant during the processing may be completely the same, so as to estimate the processing time of the second etchant to process the layer to be etched, that is, to set the second preset time.

[0063] As an example, after being treated with the second etchant, the thickness range of the thinned layer to be etched is Preferably, after being treated with the second etchant, the thickness of the layer to be etched is reduced to

[0064] Specifically, after the second etchant processes the layer to be etched, the thickness of the layer to be etched after treatment is measured, and then based on the thickness of the layer to be etched after treatment by the first etchant and the set second preset time, the etching rate of the second etchant under the corresponding etching parameters can be calculated.

[0065] Specifically, before measuring the current value of the thickness of the layer to be etched, the first etchant is used to treat the layer to be etched for the first preset time to remove the portion of the upper surface layer of the layer to be etched with poor quality, thereby improving the uniformity of the quality of the remaining portion of the layer to be etched. After measuring the current value of the thickness of the layer to be etched, the second etchant is used to treat the layer to be etched for the second preset time under the preset etching parameters, and the etching rate of the second etchant corresponding to the preset etching parameters is calculated. Since the portion of the upper surface layer of the layer to be etched with poor quality is removed, the quality uniformity of the remaining layer to be etched is better, and the etching rate fluctuation during the treatment with the second etchant is smaller, thereby improving the uniformity of the etching rate during the etching process and reducing the error of the calculated etching rate.

[0066] The etching rate measurement method of the present embodiment improves the method for measuring the etching rate. Before measuring the current value of the thickness of the layer to be etched, the first etchant is used to treat the layer to be etched for the first preset time to remove the layer to be etched with poor surface quality on the layer to be etched, thereby improving the uniformity of the quality of the remaining layer to be etched. After measuring the current thickness value of the layer to be etched, the second etchant is used to treat the layer to be etched for a second preset time under the preset etching parameters, the thickness of the layer to be etched after the treatment with the second etchant is measured, and the etching rate of the second etchant corresponding to the preset etching parameters is calculated. Since the quality of the layer to be etched after being treated with the first etchant is improved, the uniformity of the etching rate during the treatment with the second etchant is improved, and the error of the etching rate of the second etchant corresponding to the preset etching parameters is reduced.

[0067] Embodiment 2

[0068] This embodiment provides a wafer pre-cleaning process, wherein the pre-cleaning time of the wafer pre-cleaning process is set based on the etching rate measured by the etching rate measurement method described in the first embodiment.

[0069] Specifically, since the bottom of the contact hole in the wafer is exposed to the air during the device manufacturing process, a natural oxide layer will be produced, which affects the subsequent deposition of the metal layer and the contact between the metal layer and the wafer at the bottom of the contact hole. The wafer before metallization is pre-cleaned to remove contaminants on the upper surface of the wafer and the natural oxide layer on the surface of the wafer at the bottom of the contact hole, so that the upper surface of the wafer has good cleanliness, while ensuring good contact between the metal layer and the wafer at the bottom of the contact hole.

[0070] Specifically, since the natural oxide layer on the wafer surface at the bottom of the contact hole needs to be removed during the pre-cleaning process, when measuring the etching rate using the etching rate measurement method in Example 1, the material of the layer to be etched is selected to be silicon oxide, which is the same material as the oxide layer on the wafer surface, to ensure the accuracy of the etching rate measurement.

[0071] Specifically, during the wafer pre-cleaning process, the second etchant and the preset etching parameters in Example 1 are used as the etchant and etching process parameters of the wafer pre-cleaning process, respectively, to ensure that during the wafer pre-cleaning process, the actual etching rate of the pre-cleaning etchant is close to the etching rate measured in Example 1, thereby reducing the error between the actual etching rate in the pre-cleaning process and the etching rate measured in Example 1.

[0072] Specifically, the pre-cleaning time is set based on the thickness of the wafer that needs to be thinned during the pre-cleaning process and the etching rate measured by the etching rate measurement method described in Example 1. Since the error between the etching rate measured in Example 1 and the actual pre-cleaning etching rate is reduced, the error between the etching thickness during the pre-cleaning process and the preset etching thickness can be reduced, thereby improving the uniformity of the thickness of the wafer after pre-cleaning and the uniformity of the etching thickness between different batches of wafers after the pre-cleaning process.

[0073] Specifically, Figure 3 As shown, it is a statistical chart of the thickness uniformity of different batches of wafers pre-cleaned by the wafer pre-cleaning process of the present invention and the average thickness of different batches of wafer pre-cleaning etching. It can be seen from the figure that the pre-cleaning time and the pre-cleaning etching process parameters are set by the etching rate measured based on the etching rate measurement method described in Example 1. After pre-cleaning, the fluctuation range of the thickness uniformity of different batches of wafers is reduced relative to the fluctuation range of the thickness uniformity of wafers without improved process, and the uniformity of the average etched thickness of wafers after pre-cleaning between different batches is reduced from 12% to 5.68%, and the uniformity of the thickness of different batches of wafers is increased from 4.97% to 4.47%, which significantly improves the uniformity of the thickness of the wafers after pre-cleaning and the uniformity of the etching thickness between different batches of wafers.

[0074] The wafer pre-cleaning process of this embodiment sets the pre-cleaning time based on the etching rate measured by the etching rate measurement method described in Example 1, and uses the preset etching parameters and the second etchant in Example 1 as the etching process parameters and etchant of the pre-cleaning process, respectively, which significantly improves the uniformity of the thickness of the wafer after pre-cleaning and the uniformity of the etching thickness between different batches of wafers.

[0075] In summary, the etching rate measurement method and wafer pre-cleaning process of the present invention improve the etching rate measurement method. After forming the layer to be etched and before measuring the current value of the thickness of the layer to be etched, the first etchant is used to treat the layer to be etched to remove the poor quality portion of the upper surface layer of the layer to be etched, thereby improving the uniformity of the quality of the layer to be etched. After measuring the thickness of the layer to be etched after treatment with the first etchant, the second etchant is used to treat the layer for a second preset time under preset etching parameters, and then the final value of the thickness of the layer to be etched after treatment with the second etchant is measured, and the etching rate of the second etchant under the preset etching parameters is calculated. Due to the improvement of the uniformity of the quality of the layer to be etched, the uniformity of the etching rate during the etching process of the second etchant is improved, and the error of the measured etching rate is reduced. In addition, the etching rate measurement method is applied to the wafer pre-cleaning process, and the pre-cleaning time in the wafer pre-cleaning process is set based on the etching rate measured by the etching rate measurement method, and the etchant and etching process parameters in the pre-cleaning process respectively use the second etchant and the preset etching parameters, which significantly improves the uniformity of the thickness of the wafer after pre-cleaning and the uniformity of the etching thickness between wafers of different batches. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0076] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for measuring an etching rate, characterized in that: The following steps are involved: Providing a substrate, and forming a to-be-etched layer with a preset thickness on the upper surface of the substrate; Treating the layer to be etched on the upper surface of the substrate with a first etchant for a first preset time to reduce the layer to be etched on the substrate to a preset thickness; Measuring a current value of the thickness of the layer to be etched after being treated with the first etchant, and treating the layer to be etched on the upper surface of the substrate with a second etchant under preset etching parameters for a second preset time; The final value of the thickness of the layer to be etched after being treated with the second etchant is measured, and based on the difference in thickness of the layer to be etched before and after being treated with the second etchant, the etching rate of the second etchant corresponding to the preset etching parameters is calculated.

2. The etching rate measurement method according to claim 1, characterized in that: Before forming the layer to be etched, the method further includes measuring the thickness of the substrate. The thickness of the layer to be etched is the difference between the sum of the thicknesses of the substrate and the layer to be etched and the thickness of the substrate.

3. The etching rate measurement method according to claim 1, characterized in that: The state of the first etchant includes one of a liquid state and a gaseous state; the components of the second etchant include at least argon gas.

4. The etching rate measurement method according to claim 1, characterized in that: The material of the layer to be etched includes silicon, silicon oxide, silicon nitride, and silicon oxynitride.

5. The method for measuring etching rate according to claim 1, characterized in that: The first etchant and the second etchant have the same component.

6. The etching rate measurement method according to claim 1, characterized in that: The range of the pre-thickness is 7. The etching rate measurement method according to claim 1, characterized in that: The instrument for measuring the layer to be etched comprises a non-contact thickness gauge.

8. The etching rate measurement method according to claim 1, characterized in that: After being treated by the second etchant, the thickness of the layer to be etched is reduced to 9. The etching rate measurement method according to claim 1, characterized in that: After measuring the current value of the thickness of the layer to be etched after being treated with the first etchant, before using the second etchant to treat the layer to be etched for the second preset time, the method also includes placing the substrate treated with the first etchant in a process chamber of an etching machine.

10. A wafer pre-cleaning process, characterized in that: The pre-cleaning time of the wafer pre-cleaning process is set based on the etching rate measured by the etching rate measurement method according to any one of claims 1 to 9.

Images