TW201405661A - Method for removing optical resist - Google Patents

Abstract

The invention discloses a method for removing an optical resist. In the method, by using the principle that the removal uniformity of the optical resist is obviously changed because the difference between the removal rate of the optical resist at edges and the removal rate of the optical resist in the center is reduced when pressure changes in a specific pressure range and/or source power changes in a specific source power range during the removal of the optical resist, the removal uniformities of a plurality of the optical resists are obtained and the pressure and the source power corresponding to the removal uniformity of the smallest optical resist are obtained; and the removal process conditions of the optical resist are set according to the obtained pressure and the obtained source power so that the optical resist on a semiconductor on which circuit images are to be formed can be removed more uniformly.

Description

Photoresist removal method

The present invention relates to the removal of photoresist, and more particularly to a method for uniformly removing photoresist.

In semiconductor device fabrication techniques, a mask pattern on a reticle is typically transferred to a photoresist layer on the surface of the semiconductor structure using a photolithographic process. The basic processes of photolithography generally include steps of gluing, exposure, and development. The purpose of the coating is to establish a thin, uniform, and defect-free photomask layer on the surface of the semiconductor structure; the purpose of the exposure is to transfer the mask pattern into the photoresist layer by using an exposure light source; the development is performed in the photoresist layer. The exposed or unexposed regions are removed to form a patterned photoresist layer on the surface of the semiconductor structure. After the patterned photoresist layer is formed, the semiconductor structure can be etched using the patterned photoresist layer as a mask, thereby transferring the mask pattern into the semiconductor structure, thereby forming a circuit pattern in the semiconductor structure.

The photoresist layer needs to be removed after the formation of the circuit pattern in the semiconductor structure. The conventional method for removing the photoresist layer is plasma dry stripping: the semiconductor structure with the photoresist layer is placed in the plasma processing chamber, and the ashing gas is introduced into the plasma processing chamber. The ashing gas is dissociated into a plasma by an electric field between the electrodes, and the plasma reacts with the photoresist to remove the photoresist. However, the existing method of removing photoresist often has the problem of uneven photoresist removal, that is, the removal rate of the photoresist at different positions is different, resulting in partial photoresist not being completely removed, and another portion. The photoresist has been completely removed to expose the underlying semiconductor structure. Further research has also found that the removal uniformity of existing photoresists is generally poor. If you want to ensure that the photoresist above the semiconductor structure does not remain, you need to continue The plasma is generated, which inevitably causes the semiconductor structure from which the upper photoresist has been removed to continue to be exposed to the plasma environment, so that the surface of the semiconductor structure is damaged.

The technical problem to be solved by the present invention is to make the removal of the photoresist on the semiconductor structure on which the circuit pattern is to be formed more uniform.

In order to solve the above problems, the present invention provides a method for removing a photoresist, comprising: (a) determining a pressure range and a power supply range required for removing the photoresist; and (b) selecting M different in the pressure range; The pressure value is, in order, the first pressure, the second pressure, ..., the M-1 pressure, the M pressure, and M is an integer greater than 1, and selects N different power values in the power range. , which are respectively the first power source, the second power source, ..., the N-1th power, and the Nth power, N being an integer greater than 1, and the M different pressure values and the N Different power supply power values are combined to obtain M×N process parameter combinations; (c) a semiconductor structure having a photoresist formed on the surface is placed in a plasma processing chamber, and the plasma processing chamber is provided The upper electrode and the lower electrode are oppositely disposed, and the upper electrode or the lower electrode is electrically connected to the radio frequency power source, and the ashing gas containing nitrogen is introduced into the plasma processing chamber at a preset flow rate to control the plasma processing chamber. Room pressure and power supply a rate is supplied to an upper electrode or a lower electrode connected to the radio frequency power source, and a plasma is generated between the upper electrode and the lower electrode to etch the photoresist, the pressure and power supply power complying with the M×N processes Any one of the parameter combinations, after etching for a period of time, stopping the removal of the photoresist, measuring the removal rate of the photoresist at a plurality of positions, to calculate the first removal uniformity of the photoresist; (d) repeating the steps (c) M×N-1 times, ensuring that the process parameter combinations used in the step (c) of M×N times are different from each other, thereby sequentially obtaining the second removal uniformity of the photoresist, ..., the first M×N-1 removal uniformity, M×N removal uniformity; (e) comparing the first removal uniformity, the second removal uniformity, ..., the M×N-1 removal uniformity, the M×N removal uniformity, and the pressure corresponding to the minimum removal uniformity And the power source power is respectively used as the optimal pressure and the optimum power source; (f) placing the semiconductor structure on the surface on which the photoresist is formed, into the plasma processing chamber, into the plasma processing chamber Passing an ashing gas containing nitrogen gas, controlling a pressure of the plasma processing chamber to the optimum pressure, and supplying the optimal power source power to an upper electrode or a lower electrode connected to the radio frequency power source, A plasma is generated between the upper electrode and the lower electrode to remove the photoresist.

Optionally, the pressure range is from 10 mTorr to 500 mTorr, and the power source power range is greater than 0 and not greater than 1500 W.

Optionally, the ashing gas further comprises hydrogen.

Optionally, the flow rate of the nitrogen gas is not more than 1000 sccm, and the flow rate of the hydrogen gas is not more than 1500 sccm.

Optionally, the frequency of the radio frequency power source is 500KMZ~13.56MHZ.

Optionally, the calculation formulas of the first removal uniformity, the second removal uniformity, ..., the M×N-1 removal uniformity, and the M×N removal uniformity are all: (the highest removal rate-lowest Removal rate) / (2 × removal rate average).

Compared with the prior art, the present invention has the following advantages: in the process of removing the photoresist, when the pressure varies within a specific pressure range and/or the power supply power varies within a specific power supply range, the edge position photoresist The difference between the removal rate and the removal rate of the central position photoresist is reduced, so that the removal uniformity of the photoresist is significantly changed, thereby obtaining a plurality of photoresists by continuously adjusting the pressure and/or power supply. The uniformity of removal, the pressure and power supply corresponding to the minimum uniformity of photoresist removal are obtained, and the removal process conditions of the photoresist are set according to the obtained pressure and power supply, so that the light on the semiconductor device to be formed into the circuit pattern The engraving is more evenly removed.

100‧‧‧ Plasma processing unit

110‧‧‧ Plasma processing chamber

120‧‧‧Support table

121‧‧‧matcher

122‧‧‧RF power supply

130‧‧‧Semiconductor structure

140‧‧‧Electrostatic suction cup

150‧‧‧Sprinkler

151‧‧‧Air intake

152‧‧‧ stomata

160‧‧‧ venting holes

161‧‧‧vacuum pump

1 is a schematic view showing the structure of a plasma processing apparatus; and FIG. 2 is a graph showing the relationship between the pressure and the removal rate of the photoresist.

As mentioned above, conventional methods of removing photoresist often have problems in that the photoresist is not uniformly removed.

According to the inventors' research, one of the important reasons for the unevenness of photoresist removal is that the photoresist removal rate at the edge position is slower than that of the photoresist located at the center. Therefore, in order to improve the removal uniformity of the photoresist, it is necessary to control the photoresist removal rate at the edge position while controlling the photoresist removal rate in the central region to make the edge position photoresist. The difference between the removal rate and the removal rate of the central position photoresist is not excessive.

The inventors attempted to study the relationship between the process parameters for removing photoresist and the uniformity of photoresist removal by Design Of Experiment (DOE). In the process of conducting multiple design tests, the inventors accidentally learned that the power supply, the ash gas flow rate, and the ashing gas required to remove the photoresist are selected in the preliminary selection (the problem of uniformity of photoresist removal is not considered at this time). After the ratio of the flow rates of the various gases and the appropriate range of pressure: when the ratio of the flow rates of the various gases in the power supply, the pressure and the ashing gas is kept constant, only when the flow rate of the ashing gas is changed within the selected range of the ashing gas flow rate The removal uniformity of the photoresist is not obvious, the removal uniformity of the photoresist is very poor, and it is difficult to be lower than 3%; when the power supply, the pressure and the flow rate of the ashing gas are kept constant, only the selected ashing gas is selected. When the ratio of the flow rates of the various gases in the range of the flow rate of the various gases in the ashing gas is changed, the uniformity of the removal of the photoresist is not significantly changed, and the uniformity of the removal of the photoresist is poor, and it is difficult to be less than 3%; When the ratio of the flow rate of the various gases in the power supply, the ash gas flow rate and the ashing gas is kept constant, the removal rate of the edge position photoresist and the removal of the central position photoresist are only changed when the pressure is changed within the selected pressure range. The difference in rate will be reduced, so that the uniformity of photoresist removal is more obvious. Further, the uniformity of photoresist removal can be less than 3%; while maintaining the flow rate of ashing gas, the flow of various gases in the ashing gas The ratio and pressure are constant. When the power supply is changed within the selected power range, the difference between the removal rate of the edge position photoresist and the removal rate of the central position photoresist is reduced, and the photoresist is uniformly removed. The change of the property is more obvious. Further, the uniformity of the removal of the photoresist may be less than 3%; when the flow rate of the ashing gas and the flow rate of the various gases in the ashing gas are kept constant, the pressure is changed only within the selected pressure range. When the power supply is changed within the selected power supply range, the photoresist removal uniformity is better.

It should be noted that the inventors have also found that when the pressure is gradually changed in a range from a small to a large or a large to small within a selected pressure range, the change tendency of the photoresist removal uniformity is not gradually increased like a straight line. Or gradually decreasing, the trend of change is similar to that of waves, changing gradually and gradually decreasing in alternating ways; gradually changing the power supply in a manner from small to large or large to small within the selected power supply range At the same time, the change tendency of the photoresist removal uniformity is not gradually increased or decreased like a straight line, and the change trend is similar to that of a wave, and is gradually increased and gradually decreased in an alternating manner; When the pressure range and the selected power supply range are gradually changed from small to large or large to small, the change trend of photoresist removal uniformity is not gradually increased or gradually decreased like a straight line. Small, its changing trend is similar to that of waves, changing in a way that gradually increases and gradually decreases.

Accordingly, the inventors have proposed a method capable of uniformly removing the photoresist.

The technical solutions of the present invention will be clearly and completely described by the following embodiments in conjunction with the accompanying drawings. It is obvious that the described embodiments are only possible embodiments of the present invention. Part, not all of it. According to these embodiments, all other embodiments that can be obtained by those skilled in the art without creative labor are within the scope of the present invention.

1 is a schematic structural view of a plasma processing apparatus. In this embodiment, Capacitively Coupled Plasmas (CCP) is taken as an example. As shown in FIG. 1, the plasma processing apparatus 100 includes: a plasma processing chamber 110; a support table 120 disposed on a bottom wall of the plasma processing chamber 110, the support table 120 is used to support the semiconductor structure 130 to be processed, and Used as a lower electrode; an electrostatic chuck (ESC) 140 disposed above the support table 120. The electrostatic chuck 140 is used not only to fix the semiconductor structure 130 to be processed, but also to adjust the temperature of the semiconductor structure 130; and is disposed in the plasma processing chamber 110. The shower head 150 on the top wall, the shower head 150 is disposed opposite to the support table 120. The shower head 150 is provided with an air inlet hole 151 and a plurality of air holes 152 communicating with the air inlet hole 151. The shower head 150 is For introducing a reaction gas into the plasma processing chamber 110, and also serving as an upper electrode; a vent hole 160 disposed in the plasma processing chamber 110, the vent hole 160 being connected to the vacuum pump 161 for regulating the plasma The degree of vacuum of the chamber 110 is processed. In one embodiment, one of the upper electrode (ie, the shower head 150) and the lower electrode (ie, the support table 120) is connected to a radio frequency (RF) power source, and the other is grounded to enable between the upper electrode and the lower electrode. An electric field is generated. The lower electrode in the figure is electrically connected to the radio frequency power source 122 through the matcher 121, and the upper electrode is grounded through the plasma processing chamber 110.

The process of removing the photoresist in the plasma processing apparatus 100 is simplified. Single introduction: First, a semiconductor structure 130 having a photoresist formed on the surface thereof is placed on the electrostatic chuck 140, and the gas in the plasma processing chamber 110 is extracted by the vacuum pump 161 to maintain the desired degree of vacuum; The suction cup 140 applies a voltage to cause the semiconductor structure 130 to be closely adsorbed on the electrostatic chuck 140, and at the same time, an ashing gas is introduced into the plasma reaction chamber 110 through the gas inlet hole 151 until the plasma processing chamber 110 reaches the desired level. Pressure; then, using the RF power source 122 to apply power to the lower electrode (ie, the support table 120), such that the upper and lower electrodes An electric field is generated between the gas and the gas is dissociated into a plasma, and the generated plasma can react with the photoresist to remove the photoresist.

As mentioned before, during the process of removing the photoresist, when the pressure is within a specific pressure range When the variation and/or power supply varies over a particular power supply range, the photoresist removal uniformity can vary significantly. Therefore, the removal uniformity of the photoresist can be changed by controlling the pressure and/or power of the power.

First, determine the pressure range and power supply range required to remove the photoresist.

The pressure range and power supply power range required for removing the photoresist can be obtained by means well known to those skilled in the art. In an actual process, those skilled in the art can obtain the photoresist removal according to their own experience. The required pressure range and power supply range. In one embodiment of the invention, the pressure range is from 10 mTorr to 500 mTorr, and the power supply power range is greater than 0 and no greater than 1500 W. Preferably, the frequency of the radio frequency power source is from 500 KMZ to 13.56 MHz, such as 2 MHz.

Specifically, the method for determining the pressure range required to remove the photoresist may be: introducing an ashing gas into the plasma processing chamber until a certain pressure value is reached, and generating between the upper and lower electrodes in the plasma processing chamber. Plasma, observe the uniformity of the plasma. If the uniformity of the plasma meets the requirements, the pressure used meets the requirements. After multiple tests with different pressures, multiple required pressures can be obtained. The pressure can constitute the pressure range.

Specifically, the method for determining the power supply range required for removing the photoresist may be: the removal rate of the photoresist is mainly affected by the flow rate of the ashing gas and the power of the power source, and after the removal rate required for the photoresist is preset, First, determine the flow rate of the ashing gas. The flow rate of the ashing gas needs to be within the range of the gas flow meter to adjust the power of the power supply. If the removal rate of the photoresist is within the required removal rate, the power supply used is consistent. It is required that after performing multiple tests with different power sources, a plurality of power sources that meet the requirements can be obtained, and the plurality of required powers are required. The source power can constitute the power range of the power supply.

Then, a semiconductor structure having a photoresist formed on the surface is placed on the plasma In the processing chamber, the plasma processing chamber is provided with an upper electrode and a lower electrode disposed opposite to each other, and the upper electrode or the lower electrode is electrically connected to the RF power source. In this embodiment, the lower electrode is electrically connected to the radio frequency power source, and the upper electrode is grounded. The semiconductor structure is not limited to a semiconductor structure to be formed into a circuit pattern as long as it can serve as a carrier for supporting the photoresist. The photoresist on the surface of the semiconductor structure may be a photoresist that has not been patterned. In this embodiment, the semiconductor structure is a wafer having a diameter of 300 mm, and the entire surface of the wafer is coated with a photoresist.

Then, a nitrogen containing ash is introduced into the plasma processing chamber at a preset flow rate. a gas, controlling a pressure of the plasma processing chamber to be a first pressure, and supplying the first power source to an upper electrode or a lower electrode connected to the RF power source. In this embodiment, the first power source is supplied to the lower electrode, A plasma is generated between the upper electrode and the lower electrode, and the photoresist is removed by the plasma. After a period of time, the photoresist is stopped to be removed, and the removal rate of the photoresist at a plurality of positions is measured to calculate the light. The first removal uniformity of the glue.

In one embodiment of the invention, the ashing gas contains, in addition to nitrogen, Includes hydrogen. When the photoresist is removed, the flow rate of nitrogen gas is not more than 1000 sccm, and the flow rate of hydrogen gas is not more than 1500 sccm. The first pressure is within the pressure range, and the first power source is within the power source range. As described above, the photoresist removal rate at the edge position is slower than that of the photoresist located at the center position. Therefore, in order to more accurately reflect the removal uniformity of the photoresist, preferably, The several locations are evenly arranged on the diameter of the wafer. And the greater the number of the plurality of locations, the more uniform the photoresist removal uniformity obtained. In this embodiment, the semiconductor structure is a wafer having a diameter of 300 mm and the entire surface of the wafer is coated with a photoresist, and 49 positions can be selected along the diameter direction of the wafer, and 49 positions are arranged from the center of the wafer to the edge of the wafer. . Further, 49 positions can be arranged at equal intervals.

Then, a semiconductor structure having a photoresist formed on the surface is placed on the plasma In the processing chamber, the nitrogen gas-containing ashing gas is introduced into the plasma processing chamber at the predetermined flow rate, the pressure of the plasma processing chamber is controlled to be a second pressure, and the second power source is supplied to An upper electrode or a lower electrode connected to the RF power source to change the uniformity of removal of the photoresist. In this embodiment, the second power source is supplied to the lower electrode, and a plasma is generated between the upper electrode and the lower electrode. The photoresist is removed by the action of the body. After a period of time, the photoresist is stopped from being removed, and the removal rate of the photoresist at the plurality of locations is measured to calculate a second removal uniformity of the photoresist. It should be noted that the photoresist on the semiconductor structure is reformed in this step.

The second pressure is within the pressure range, and the second power source is in the Within the power range. When the second pressure and the second power source are different, the first pressure, the first power, in other words, the first pressure is not equal to the second pressure, or the second power is The first power sources are not equal, or the first pressure is not equal to the second pressure and the second power is not equal to the first power. It should be noted that several positions on the photoresist when obtaining the second removal uniformity of the photoresist are required to be the same as the positions on the photoresist when the first removal uniformity of the photoresist is obtained. In addition, the flow rate of the ashing gas used in obtaining the second removal uniformity of the photoresist is the same as the flow rate of the ashing gas used to obtain the first uniformity of removal of the photoresist, when the ashing gas contains at least two gases. The ashing gas flow rate refers to the flow rate of various ashing gases.

When the third removal uniformity is obtained according to the above method, the fourth removal is uniform Sex, ... X (X is an integer greater than 2) When uniformity is removed, minimal removal uniformity can be found, and the minimum removal uniformity is easily less than 3%. It can be seen that the pressure and/or power used to remove the photoresist can have a significant effect on the uniformity of photoresist removal.

The removal uniformity of the photoresist can be obtained by various calculation methods. In one embodiment of the present invention, the calculation formula of the first and second removal uniformity can be: (highest removal rate - minimum removal rate) / ( 2× removal rate average).

The above conclusions of the present invention are explained below by specific test data and test charts.

In Tables 1 to 5 below, nitrogen and hydrogen are used to remove the diameter of 300mm. The photoresist on the wafer, the photoresist covers the entire surface of the wafer, 49 positions along the diameter direction of the wafer, 49 positions are arranged from the center of the wafer to the edge of the wafer, and 49 positions are equal. The pitch was arranged, the photoresist removal rate at 49 positions was measured, and the removal uniformity in the table was obtained as described above.

As shown in Table 1, in the test of removing the photoresist twice, the pressure and power supply were maintained. The power is constant, only the flow rate of nitrogen and hydrogen in the ashing gas is changed (the flow rate of nitrogen is adjusted from 250 sccm to 75 sccm, the flow rate of hydrogen is adjusted from 250 sccm to 75 sccm), and the uniformity of photoresist removal is only changed by 0.2%. The change was not obvious and the removal uniformity of the photoresist was higher than 3%.

As shown in Table 2, in the test of removing the photoresist twice, the pressure and power supply were maintained. The power is constant, only the flow ratio of nitrogen to hydrogen in the ashing gas is changed (the flow ratio of nitrogen to hydrogen is adjusted from 3:1 to 1:1), and the uniformity of photoresist removal is only changed by 0.2%. Obviously, the photoresist removal uniformity is higher than 3%.

As shown in Table 3, in the test of removing the photoresist twice, the pressure, nitrogen flow rate and hydrogen flow rate were kept unchanged, and only the power supply was changed (the power supply was adjusted from 800 W to 500 W), and the photoresist uniformity was removed. Changed by 1.2%, the change was obvious.

table 3

As shown in Table 4, in the test of removing the photoresist four times, the pressure, nitrogen flow rate and hydrogen flow rate were kept unchanged, and only the power supply was changed (the power supply was adjusted from 550 W to 500 W, 450 W, 400 W in sequence), and lithography was performed. The removal uniformity of the glue changed by more than 1%, and the change was obvious, and as shown in the second and third sets of test data, the removal uniformity of the photoresist was less than 3%. When the power supply is gradually reduced, the removal uniformity of the photoresist is first reduced from 3.4% to 2.1%, then increased to 2.6%, and then increased to 4.0%, in other words, when the power supply is gradually increased or decreased. In the hour, the change tendency of the removal uniformity of the photoresist is similar to that of the wave, and is gradually increased and gradually decreased in an alternating manner, without gradually increasing or decreasing like a straight line.

It can be seen from Tables 3 and 4 that the minimum removal uniformity can be obtained when the power supply is continuously adjusted to perform multiple tests. It will be appreciated by those skilled in the art that the specific number of trials should not be limited to the embodiments of the invention.

As shown in Table 5, in the test of removing the photoresist three times, the power supply, the nitrogen flow rate, and the hydrogen flow rate were kept unchanged, and only the pressure was changed (the pressure was sequentially adjusted from 200 mTorr to 210 mTorr, 230 mTorr), and the photoresist was uniformly removed. The change in sex was greater than 1.5% and the change was significant. When the pressure is gradually increased, the removal uniformity of the photoresist is first reduced from 5.0% to 3.5%, and then increased to 8.6%. In other words, when the pressure is gradually increased or decreased, the uniformity of removal is changed. Similar to waves, changing in a way that gradually increases and gradually decreases, not similar The line gradually increases or decreases gradually.

As can be seen from Table 5, the minimum removal uniformity can be obtained when the pressure is continuously adjusted to perform multiple tests. It will be appreciated by those skilled in the art that the specific number of trials should not be limited to the embodiments of the invention.

Combined with Tables 3, 4, and 5, it can be seen that the minimum removal uniformity can be obtained when the pressure and power supply are continuously adjusted to perform multiple tests. For example, in one embodiment, when the pressure is 200 mTorr, the power supply is 500 W, the nitrogen flow rate is 150 sccm, and the hydrogen flow rate is 150 sccm, the photoresist removal uniformity is 2.1%, less than 3%.

2 is a graph showing the relationship between the pressure and the photoresist removal rate. FIG. 2 is the origin of the wafer (ie, the semiconductor structure) as the coordinate origin, and the diameter of the wafer is the abscissa, and the photoresist removal rate is used. As the ordinate, as shown in Fig. 2, under the same process conditions (power supply power is 500W, nitrogen flow rate is 150sccm, hydrogen flow rate is 150sccm), the removal rate of photoresist at different positions is not equal, and the photoresist at the center position In contrast, the removal rate of the photoresist at the edge position is slow, and when the pressure is changed only, the removal uniformity of the photoresist changes significantly.

In view of the above, a method for removing a photoresist may be proposed: firstly, the removal uniformity of the photoresist is changed according to the above, and when the uniformity of removal of the photoresist is minimized, the pressure and power supply used may be correspondingly obtained, and then, The photoresist removal process conditions are set according to the obtained pressure and power supply power, so that the photoresist on the semiconductor device to be formed into the circuit pattern is more uniformly removed.

First, step (a) is performed to determine the pressure range and power supply range required to remove the photoresist.

The pressure range and power supply power range required for removing the photoresist can be obtained by means well known to those skilled in the art. In an actual process, those skilled in the art can obtain the photoresist removal according to their own experience. The required pressure range and power supply range. In one embodiment of the invention, the pressure range is from 10 mTorr to 500 mTorr, and the power supply power range is greater than 0 and no greater than 1500 W. Preferably, the frequency of the RF power source is 500KMZ~13.56MHZ, such as 2MHZ.

Specifically, the pressure range and power supply power range required to remove the photoresist can be determined in the manner previously described.

Then, step (b) is performed to select M different pressure values within the pressure range, which are respectively a first pressure, a second pressure, ..., an M-1 pressure, and an M pressure, and M is greater than 1 An integer that selects N different power supply values in the power supply range, which are respectively the first power, the second power, ..., the N-1 power, and the N power, and N is greater than An integer of 1, combining the M different pressure values with the N different power supply values to obtain M×N process parameter combinations.

Since the M pressure values are different from each other and the N power source values are different from each other, the M×N process parameter combinations are also different from each other.

Then, performing step (c), placing a semiconductor structure having a photoresist formed on the surface thereof in the plasma processing chamber, wherein the plasma processing chamber is provided with oppositely disposed upper electrodes, lower electrodes, upper electrodes or lower electrodes Electrically connecting with the RF power source, introducing a ashing gas containing nitrogen into the plasma processing chamber at a preset flow rate, controlling the pressure of the plasma processing chamber, and supplying power to the RF power source. The upper electrode or the lower electrode is configured such that the pressure and the power supply power conform to any one of the M×N process parameter combinations, and a plasma is generated between the upper electrode and the lower electrode, and after a period of time, the photolithography is stopped. Glue, measuring the removal rate of the photoresist at a number of locations to calculate the first removal uniformity of the photoresist. In this embodiment, the power source is supplied to the lower electrode and the upper electrode is grounded.

The semiconductor structure is not limited as long as it can serve as a carrier for supporting the photoresist. It is a semiconductor structure to be formed into a circuit pattern. The photoresist on the surface of the semiconductor structure may be a photoresist that has not been patterned. In this embodiment, the semiconductor structure is a wafer having a diameter of 300 mm, and the entire surface of the wafer is coated with a photoresist.

In one embodiment of the invention, the ashing gas contains, in addition to nitrogen, Includes hydrogen. When the photoresist is removed, the flow rate of nitrogen gas is not more than 1000 sccm, and the flow rate of hydrogen gas is not more than 1500 sccm. As described above, the photoresist removal rate at the edge position is slower than that of the photoresist located at the center position. Therefore, in order to more accurately reflect the removal uniformity of the photoresist, preferably, the Several locations are evenly arranged across the diameter of the wafer. And the greater the number of the plurality of locations, the more uniform the photoresist removal uniformity obtained. In this embodiment, the semiconductor structure is a wafer having a diameter of 300 mm and the entire surface of the wafer is coated with a photoresist, and 49 positions can be selected along the diameter direction of the wafer, and 49 positions are arranged from the center of the wafer to the edge of the wafer. . Further, 49 positions can be arranged at equal intervals.

Then, step (d) is performed, and the step (c) is repeated M×N-1 times to ensure The process parameter combinations used in the step (c) of the M×N times are different from each other, that is, there is no case where the pressure and the power source used in the step (c) are equal when M×N times are performed, thereby The second removal uniformity of the photoresist, ..., the M×N-1 removal uniformity, and the M×N removal uniformity are sequentially obtained.

It should be noted that the first removal uniformity of the photoresist is obtained, and the second removal is uniform. Sex, ..., M x N-1 removal uniformity, M × N removal uniformity, several positions on the photoresist are the same, and lithography on the semiconductor structure each time the photoresist removal uniformity is measured The glue is reformed. In addition, obtaining the first removal uniformity of the photoresist, the second removal uniformity, ..., the M×N-1 removal uniformity, and the M×N removal uniformity are the same as the ash gas flow rate when the ash is obtained. When the gas contains at least two gases, the ash gas flow rate refers to the flow rate of various ashing gases.

Then, performing step (e), comparing the obtained first removal uniformity, Second, the uniformity, ..., the M×N-1 removal uniformity, the M×N removal uniformity, and the pressure and power supply power corresponding to the minimum removal uniformity are respectively used as the optimal pressure and the optimal power.

Finally, step (f) is performed to form a circuit diagram of the photoresist to be formed on the surface a semiconductor structure is disposed in the plasma processing chamber, an ashing gas containing nitrogen gas is introduced into the plasma processing chamber, a pressure of the plasma processing chamber is controlled to be the optimal pressure, and the The optimum power supply is supplied to an upper or lower electrode connected to the RF power source, and a plasma is generated between the upper electrode and the lower electrode to remove the photoresist. In this embodiment, the optimum power supply is supplied to the lower electrode and the upper electrode is grounded.

The specific size of the M and N may be adjusted as the case may be, when the pressure, When the power supply range is wide, in order to reduce the number of executions of step (c), the M and N values may be smaller; conversely, when the pressure and the power supply range are narrow, in order to obtain the optimal pressure, the most The power of the power supply is more accurate, and the M and N values can be larger.

The uniformity of photoresist removal can be obtained by various calculation methods, in the present invention In one embodiment, the first removal uniformity, the second removal uniformity, ..., the M×N-1 removal uniformity, and the M×N removal uniformity are all calculated as: (the highest removal rate - Minimum removal rate) / (2 × removal rate average).

In summary, the present invention has the following advantages over the prior art:

During the process of removing the photoresist, when the pressure changes within a specific pressure range and / Or when the power of the power varies within a specific power supply range, the difference between the removal rate of the photoresist at the edge position and the removal rate of the photoresist at the center position is reduced, and the uniformity of photoresist removal is significantly changed. The uniformity of removal of multiple photoresists can be obtained by continuously adjusting the pressure and/or power supply, obtaining the minimum pressure and power supply corresponding to the uniformity of photoresist removal, and setting the light according to the obtained pressure and power supply. The removal process conditions of the engraving make the photoresist removal on the semiconductor device to be formed into a circuit pattern more uniform.

The above description of the embodiments should enable those skilled in the art to better The invention is understood and the invention can be reproduced and used. Various changes and modifications of the above-described embodiments will be apparent to those skilled in the <RTIgt; Therefore, the present invention should not be construed as limited to the embodiments described herein, and the scope of the invention should be defined by the appended claims.

Claims (6)

A method for removing a photoresist, comprising: (a) determining a pressure range required to remove the photoresist and a power supply range; (b) selecting M different pressure values within the pressure range, in turn The first pressure, the second pressure, the ..., the M-1 pressure, the M pressure, M is an integer greater than 1, and select N different power values in the power range of the power supply, respectively The first power source, the second power source, ..., the N-1th power, and the Nth power, N is an integer greater than 1, and the M different pressure values are different from the N different power sources The values are combined to obtain M×N process parameter combinations; (c) the semiconductor structure having the photoresist formed on the surface is placed in a plasma processing chamber, wherein the plasma processing chamber is provided with a relative An upper electrode and a lower electrode are disposed, and the upper electrode or the lower electrode is electrically connected to a radio frequency power source, and a nitrogen gas containing ash gas is introduced into the plasma processing chamber to control plasma at a preset flow rate. Body processing chamber pressure and power a rate is supplied to the upper electrode or the lower electrode connected to the RF power source, and a plasma is generated between the upper electrode and the lower electrode to etch the photoresist, the pressure and the power supply comply with the Any one of M×N process parameter combinations, after etching for a period of time, stopping removing the photoresist, measuring the removal rate of the photoresist at a plurality of positions, to calculate the first removal uniformity of the photoresist; (d Repeating the step (c) M×N-1 times to ensure that the process parameter combinations used in the step (c) of the M×N times are different from each other, thereby sequentially obtaining the second removal uniformity of the photoresist. , M×N-1 removal uniformity, M×N removal uniformity; (e) comparison of the first removal uniformity, second removal uniformity, ..., M×N- 1 removal uniformity, M×N removal uniformity, the pressure and power supply power corresponding to the minimum removal uniformity are taken as the optimal pressure and the optimal power supply respectively; (f) placing a semiconductor structure on the surface of which a photoresist is formed to form a circuit pattern in the plasma processing chamber, and introducing an ashing gas containing nitrogen into the plasma processing chamber to control the plasma The pressure of the body processing chamber is the optimal pressure, and the optimal power source is supplied to the upper electrode or the lower electrode connected to the RF power source, and the upper electrode and the lower electrode are A plasma is generated to remove the photoresist. The method of claim 1, wherein the pressure range is from 10 mTorr to 500 mTorr, and the power range of the power source is greater than 0 and not greater than 1500 W. The method of claim 1, wherein the ashing gas further comprises hydrogen. The method of claim 3, wherein the flow rate of the nitrogen gas is not more than 1000 sccm, and the flow rate of the hydrogen gas is not more than 1500 sccm. The method of claim 1, wherein the frequency of the radio frequency power source is 500 KMZ to 13.56 MHz. The method of claim 1, wherein the first removal uniformity, the second removal uniformity, ..., the M×N-1 removal uniformity, and the calculation formula of the M×N removal uniformity are both It is: (highest removal rate - lowest removal rate) / (2 x removal rate average).