JP2021068791A - Method for manufacturing semiconductor device - Google Patents

Abstract

To provide a method for manufacturing a semiconductor device, by which reduction in a function of removing a resist can be suppressed.SOLUTION: A plurality of semiconductor substrates is processed by repeating steps of preparing a semiconductor substrate having one surface, disposing a resist on the one surface, performing a predetermined process by use of a resist, and putting the semiconductor substrate into a mixture liquid prepared by mixing sulfuric acid and hydrogen peroxide water for cleaning so as to remove the resist. After the mixture liquid is first prepared, a step of replenishing the mixture liquid with hydrogen peroxide is performed a plurality of times. When an interval from when the mixture liquid is first prepared until the semiconductor substrate is first put into the mixture liquid is referred as a standby time Tf, and an interval in replenishing hydrogen peroxide is referred as a replenishing interval Ta, Tb, the standby time is controlled to be equal to or shorter than the longest replenishing time interval.SELECTED DRAWING: Figure 5

Description

The present invention relates to a method for manufacturing a semiconductor device, which includes cleaning a semiconductor substrate.

Conventionally, a method for manufacturing a semiconductor device including cleaning a semiconductor substrate has been proposed (see, for example, Patent Document 1). For example, when a resist is placed on a semiconductor substrate and a semiconductor device is manufactured using the resist, a step including removing the resist by cleaning the semiconductor substrate is performed.

In this case, the resist is removed using a mixed solution (SPM: Sulfuric acid and hydrogen Peroxide Mixture) in which sulfuric acid and hydrogen peroxide solution are mixed. The mixed solution contains sulfuric acid and persulfuric acid produced by the reaction of sulfuric acid and hydrogen peroxide solution. Then, when the resist is removed using the mixed liquid, the semiconductor substrate on which the resist is arranged is charged into the mixed liquid while heating the mixed liquid to a predetermined temperature and maintaining the temperature. As a result, the resist is mainly dissolved by the sulfuric acid in the mixed solution, and the resist is mainly decomposed by the persulfuric acid in the mixed solution, and the resist is peeled off.

Japanese Unexamined Patent Publication No. 2004-193407

However, when the mixed solution is heated to a predetermined temperature and maintained at that temperature, the persulfate begins to autolyze. Therefore, if the mixed solution is quickly generated before cleaning the semiconductor substrate on which the resist is arranged and maintained at a predetermined temperature, the semiconductor substrate on which the resist is arranged is excessively generated before being charged into the mixed solution. The sulfuric acid self-decomposes and the ability to peel off the resist is reduced.

In view of the above points, it is an object of the present invention to provide a method for manufacturing a semiconductor device capable of suppressing a decrease in the function of peeling a resist.

A first aspect of claim 1 for achieving the above object is a method for manufacturing a semiconductor device that peels off a resist (20), wherein a semiconductor substrate (10) having one surface (10a) is prepared, and one surface is on the surface. To remove the resist by arranging the resist in the semiconductor, performing a predetermined treatment using the resist, and putting a semiconductor substrate into a mixed solution of sulfuric acid and a hydrogen peroxide solution for cleaning. , Are processed multiple times to process a plurality of semiconductor substrates, first to generate a mixed solution, and then to replenish the mixed solution with hydrogen peroxide solution multiple times to first generate the mixed solution and then first. Assuming that the interval until the semiconductor substrate is put into the mixed solution is the standby interval (Tf) and the interval for replenishing the hydrogen peroxide solution is the replenishment interval (Ta, Tb), the standby interval is the most of the replenishment intervals. It is said to be less than a long period of time.

According to this, the waiting interval is set to be equal to or less than the longest period of each replenishment interval. Therefore, it is possible to prevent the concentration of persulfuric acid from being remarkably reduced before cleaning the first semiconductor substrate. Therefore, it is possible to suppress the deterioration of the function of peeling the resist. By setting the standby interval in this way, it is not necessary to replenish the hydrogen peroxide solution in the period from the newly generated mixed solution to the first cleaning of the semiconductor substrate, and the amount of the hydrogen peroxide solution used is eliminated. Can be suppressed from increasing.

The reference reference numerals in parentheses attached to each component or the like indicate an example of the correspondence between the component or the like and the specific component or the like described in the embodiment described later.

It is sectional drawing which shows the manufacturing process of the semiconductor device in 1st Embodiment. It is sectional drawing which shows the manufacturing process of the semiconductor device which follows FIG. 1A. It is sectional drawing which shows the manufacturing process of the semiconductor device which follows FIG. 1B. It is a schematic diagram which shows the processing tank. It is a schematic diagram which shows the reaction at the time of peeling off a resist. It is a timing chart which shows the timing of cleaning a semiconductor substrate and the timing of replenishing hydrogen peroxide solution. It is a timing chart which shows the timing of replenishing the hydrogen peroxide solution, and the concentration of sulfuric acid and persulfuric acid.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following embodiments, parts that are the same or equal to each other will be described with the same reference numerals.

(First Embodiment)
The method for manufacturing the semiconductor device of the first embodiment will be described with reference to FIGS. 1A to 1C. The method for manufacturing the semiconductor device of the present embodiment is a method for manufacturing a plurality of semiconductor devices in order. In other words, the method for manufacturing a semiconductor device of the present embodiment is a method for continuously manufacturing a plurality of semiconductor devices. Further, in the following, as a method of manufacturing a semiconductor device including cleaning a semiconductor substrate, a method of manufacturing a semiconductor device in which a diode is formed will be described.

First, as shown in FIG. 1A, a semiconductor substrate 10 made of silicon or the like and having one side 10a is prepared. In this embodiment, the semiconductor substrate 10 is P-shaped. Then, the resist 20 is arranged on one surface 10a of the semiconductor substrate 10. Subsequently, exposure and development are performed to pattern the resist 20, and an opening 21 for opening a predetermined region on one surface 10a of the semiconductor substrate 10 is formed.

Next, as shown in FIG. 1B, N-type impurities are ion-implanted using the resist 20 as a mask. Then, heat treatment is performed to activate the impurities to form the N-type region 11.

Then, as shown in FIG. 1C, the resist 20 is peeled off. As a result, a semiconductor device in which a diode is formed is manufactured. Then, in the present embodiment, a plurality of semiconductor devices are manufactured in order by performing each of the above steps in order. That is, a plurality of semiconductor devices are continuously manufactured.

Next, the process for peeling the resist 20 will be specifically described.

First, when peeling off the resist 20, as shown in FIG. 2, a mixed solution of sulfuric acid and hydrogen peroxide solution is prepared. In the present embodiment, as shown in FIG. 2, sulfuric acid and hydrogen peroxide solution are mixed in the treatment tank 30 to generate a mixed solution. The treatment tank 30 includes a heater 41 and a filter 42, and is provided with a circulation path 40 capable of circulating the mixed liquid.

Then, in the present embodiment, the mixed liquid is heated and maintained at a treatment temperature of 130 to 150 ° C. by allowing the mixed liquid to circulate in the circulation path 40. Then, the semiconductor substrate 10 on which the resist 20 is arranged is put into this mixed liquid and washed to peel off the resist 20.

In this case, first, as shown by the following chemical formula 1, persulfuric acid is produced from sulfuric acid and hydrogen peroxide solution in the mixed solution.

(Chemical formula 1) H _{2 SO 4} + H ₂ O ₂ → H ₂ SO ₅ + H ₂ O
Then, when the resist 20 is peeled off, as shown in FIG. 3, a dissolution reaction for dissolving the resist 20 (that is, a cleavage reaction) and a decomposition reaction for decomposing the resist 20 (that is, an oxidation reaction) occur. .. In this case, in the dissolution reaction, the reaction of the following chemical formula 2 mainly occurs. In the decomposition reaction, the reaction of the following chemical formula 3 mainly occurs.

（化３）Ｃ、２Ｈ＋Ｈ_２ＳＯ_４→Ｈ_２Ｏ＋ＣＯ_２＋２Ｈ_２ＳＯ_４
なお、上記化学式２において、左辺の第１項は、レジスト２０を示しており、右辺の第１項および第２項は、レジスト２０が溶解したことを示している。上記化学式２および化学式３で示されるように、レジスト２０を剥離する際には、硫酸および過硫酸の２種類の反応種が必要になる。しかしながら、過硫酸は、約８０℃程度から自己分解を始める材料であり、混合液が処理温度で維持されると、下記化学式４で示されるように自己分解する。

(Chemical 3) C, 2H + H ₂ SO ₄ → H ₂ O + CO ₂ + 2H ₂ SO ₄
In the above chemical formula 2, the first term on the left side indicates the resist 20, and the first and second terms on the right side indicate that the resist 20 has been dissolved. As shown by Chemical Formula 2 and Chemical Formula 3, two types of reactive species, sulfuric acid and persulfuric acid, are required when peeling the resist 20. However, persulfuric acid is a material that starts autolysis from about 80 ° C., and when the mixed solution is maintained at the treatment temperature, it autolyzes as shown by the following chemical formula 4.

(Chemical 4) 2H ₂ SO ₅ → 2H ₂ SO ₄ + O ₂
Therefore, when a plurality of semiconductor devices are manufactured in order by performing the steps of FIGS. 1A to 1C in order, the concentration of persulfate decreases by maintaining the mixed solution at the processing temperature. As a result, in the step of peeling the resist 20 of FIG. 1C, the function of peeling the resist 20 gradually deteriorates over time.

Therefore, in the present embodiment, as shown in FIGS. 4 and 5, the mixed solution is periodically replenished with hydrogen peroxide solution. As a result, as shown by the above chemical formula 1, persulfuric acid is periodically generated, and it is possible to prevent the step of peeling the resist 20 from being executed in a state where the concentration of persulfuric acid is lowered.

Here, in the present embodiment, the hydrogen peroxide solution is replenished before a predetermined period for processing each semiconductor substrate 10. That is, as shown in FIG. 4, for example, at the time point T4, the time point T6, and the time point T8, the semiconductor substrate 10 on which the resist 20 is arranged is put into the mixed liquid and the resist 20 is peeled off. .. In this case, the hydrogen peroxide solution is replenished at the time point T3 before the time point T4, the hydrogen peroxide solution is replenished at the time point T5 before the time point T6, and the hydrogen peroxide solution is replenished at the time point T7 before the time point T8. To replenish. As a result, when the semiconductor substrate 10 is washed and the resist 20 is peeled off at the time point T4, the time point T6, and the time point T8, it is suppressed that the concentration of persulfuric acid is low.

As shown in FIG. 5, even if the same amount of hydrogen peroxide solution is replenished, as shown in the above chemical formula 2, the concentration of sulfuric acid is also reduced by cleaning the semiconductor substrate 10, so that it is generated. The concentration of hydrogen peroxide also decreases. Therefore, when the concentration of sulfuric acid becomes less than a predetermined threshold value, the mixed solution is discarded and a new mixed solution is generated.

Then, as shown in FIG. 4, assuming that the interval between the time point T3 and the time point T5 for replenishing the hydrogen peroxide solution is the replenishment interval Ta and the interval between the time point T5 and the time point T7 is the replenishment interval Tb, the replenishment interval Ta and the replenishment The interval Tb is set based on the temperature of the mixed solution to be maintained and the like. In this embodiment, the replenishment interval Ta and the replenishment interval Tb are the same period, which is about 20 minutes.

Further, a mixed liquid is generated at a time point T1 before the semiconductor substrate 10 on which the resist 20 is arranged is first washed. In this case, if the mixed solution is generated too quickly, the concentration of persulfuric acid will drop too much when cleaning the first semiconductor substrate 10. Therefore, in the present embodiment, the waiting interval Tf between the time point T1 at which the mixed liquid is first produced and the time point T2 at which the first semiconductor substrate 10 is processed is equal to or less than the longest of the replenishment interval Ta and the replenishment interval Tb. Has been done.

In the present embodiment, since the replenishment interval Ta and the replenishment interval Tb are the same period, the waiting interval Tf is set to be equal to or less than the period of the replenishment interval Ta and the replenishment interval Tb. More specifically, the waiting interval Tf of the present embodiment is set to the same period as the replenishment interval Ta and the replenishment interval Tb. Although not particularly limited, when the mixed solution is first produced, the concentration of persulfuric acid is 5 to 6 g / L (that is, the volume ratio of sulfuric acid to persulfuric acid in the mixed solution is 2. A mixed solution is produced so as to be about 25).

As described above, in the present embodiment, the waiting interval Tf is set to be equal to or less than the longest period of the replenishment intervals Ta and Tb. Therefore, it is possible to prevent the concentration of persulfuric acid from being remarkably reduced before cleaning the first semiconductor substrate 10. Therefore, it is possible to suppress the deterioration of the function of peeling the resist 20. By setting the standby interval Tf in this way, it is not necessary to replenish the hydrogen peroxide solution in the period from the newly generated mixed solution to the first cleaning of the semiconductor substrate 10, and the hydrogen peroxide solution is eliminated. It is possible to suppress an increase in the amount used.

Further, in the present embodiment, since the hydrogen peroxide solution is replenished once before cleaning each of the semiconductor substrates 10, it is possible to suppress the deterioration of the function of peeling the resist 20 when processing each of the semiconductor substrates 10. it can. Further, since the hydrogen peroxide solution is not replenished a plurality of times before cleaning the semiconductor substrate 10, it is possible to suppress an increase in the amount of the hydrogen peroxide solution used.

Further, in the present embodiment, the waiting interval Tf and the replenishment intervals Ta and Tb are set to the same period. Therefore, the timing of replenishing the hydrogen peroxide solution and the timing of cleaning the semiconductor substrate 10 can be easily adjusted, and the manufacturing process can be simplified.

(Second Embodiment)
The second embodiment will be described. This embodiment defines the period from the time when the hydrogen peroxide solution is replenished to the time when the semiconductor substrate 10 is washed with respect to the first embodiment. Others are the same as those in the first embodiment, and thus the description thereof will be omitted here.

In the present embodiment, when cleaning the semiconductor substrate 10 after the time point T3, the period from the time when the hydrogen peroxide solution is replenished to the time when the semiconductor substrate 10 is washed next is set to be less than the standby interval Tf. .. That is, the period between the time point T3 and the time point T4, the period between the time point T5 and the time point T6, and the period between the time point T7 and the time point T8 are set to be less than the waiting interval Tf.

According to this, when the semiconductor substrate 10 is washed at the time point T4, the time point T6, and the time point T8, it is possible to suppress that the persulfate is in a dilute state, and it is possible to prevent the resist 20 from being peeled off.

(Third Embodiment)
The third embodiment will be described. In this embodiment, the amount of hydrogen peroxide solution to be replenished may be changed from the second time onward with respect to the first embodiment. Others are the same as those in the first embodiment, and thus the description thereof will be omitted here.

In the present embodiment, when replenishing the hydrogen peroxide solution after the second time, if the interval from replenishing the hydrogen peroxide solution to cleaning the semiconductor substrate 10 is equal to or longer than the standby interval Tf, the first replenishment is performed. Replenish the hydrogen peroxide solution in an amount larger than the amount of the hydrogen peroxide solution. That is, when replenishing the hydrogen peroxide solution after the time point T5, if the interval between the time point at which the hydrogen peroxide solution is replenished and the time point until the next cleaning of the semiconductor substrate 10 is equal to or greater than the standby interval Tf. Replenish the hydrogen peroxide solution in an amount larger than the amount of the hydrogen peroxide solution replenished at the time point T3.

In this case, the period from the time when the hydrogen peroxide solution is replenished from the second time onward to the time when the semiconductor substrate 10 is washed next is set to Tfa (however, Tfa> Tf), and the amount of the hydrogen peroxide solution to be replenished at the time point T3. Is Vini, and the amount of hydrogen peroxide solution to be replenished after the time point T5 is V, so that V = Vini (Tfa / Tf). That is, when the interval from the time when the hydrogen peroxide solution is replenished from the second time onward to the time when the semiconductor substrate 10 is washed next is equal to or longer than the standby interval Tf, the hydrogen peroxide solution is replenished in proportion to the elapsed time. Increase the amount to do.

According to this, when the interval from the time when the hydrogen peroxide solution is replenished to the time when the semiconductor substrate 10 is washed next becomes the standby interval Tf or more, the amount of the hydrogen peroxide solution replenished increases. Cleaning the semiconductor substrate 10 in a dilute state of hydrogen peroxide is suppressed. Therefore, it is possible to prevent the resist 20 from being peeled off.

(Fourth Embodiment)
A fourth embodiment will be described. In this embodiment, the amount of hydrogen peroxide solution replenished is determined based on the reaction temperature of the hydrogen peroxide solution with respect to the first embodiment. Others are the same as those in the first embodiment, and thus the description thereof will be omitted here.

First, by replenishing the mixed solution with hydrogen peroxide solution, persulfuric acid is produced as shown by the above chemical formula 1. In this case, heat of reaction is generated in the process of producing persulfuric acid, and the heat of reaction is proportional to the concentration of persulfuric acid produced. Then, the temperature of the mixed solution set based on the concentration of persulfuric acid required for peeling the resist 20 is set as the threshold temperature. The threshold temperature is, for example, a temperature at which a sufficient concentration of persulfate remains when the semiconductor substrate 10 is washed, considering the period between the time when the hydrogen peroxide solution is replenished and the time when the semiconductor substrate 10 is washed. It is preferable to be done.

Then, in the present embodiment, when replenishing the hydrogen peroxide solution, the temperature of the mixed solution is measured so that the measured temperature becomes equal to or higher than the threshold temperature. Specifically, when replenishing the hydrogen peroxide solution, the replenishment is stopped when the temperature of the mixed solution becomes equal to or higher than the threshold temperature.

Further, when replenishing the hydrogen peroxide solution, the hydrogen peroxide solution less than a predetermined threshold replenishment amount is replenished. That is, when replenishing the hydrogen peroxide solution, if the temperature of the mixture does not exceed the threshold temperature even if the same hydrogen peroxide solution as the threshold replenishment amount is replenished, the concentration of sulfuric acid has already decreased. Discard the mixture.

According to this, when replenishing the hydrogen peroxide solution, the temperature of the mixed solution may be equal to or higher than the threshold temperature. Therefore, the hydrogen peroxide solution is used especially at the time point T3 or the like when the semiconductor substrate 10 is started to be washed. It is possible to suppress the increase in the amount.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the claims.

For example, in the first embodiment, a method of sequentially manufacturing a plurality of semiconductor devices by sequentially processing the semiconductor substrates 10 has been described. However, in the first embodiment, a plurality of semiconductor devices 10 may be managed in lot units, and each lot may be ordered in order to manufacture a plurality of semiconductor devices in order. Further, the plurality of semiconductor substrates 10 may be washed between the time points when the hydrogen peroxide solution is replenished. For example, between the time point T3 and the time point T5 in FIG. 4, the semiconductor substrate 10 is washed at the time point T4, and the semiconductor substrate 10 is also between the time point T3 and the time point T4 or between the time point T4 and the time point T5. It may be washed.

Further, in the first embodiment, the replenishment interval Ta and the replenishment interval Tb may be set to different periods. Then, the waiting interval Tf may be set to be equal to or less than the shortest period of the replenishment intervals Ta and Tb. According to this, it is further suppressed that the concentration of persulfuric acid is lowered when the semiconductor substrate 10 is first washed. Further, the waiting interval Tf and the replenishment intervals Ta and Tb do not have to be the same period.

10 Semiconductor substrate 10a One side 20 Resist

Claims (8)

A method for manufacturing a semiconductor device that peels off the resist (20).
Preparing a semiconductor substrate (10) having one side (10a) and
Placing the resist on one surface and
Performing a predetermined treatment using the resist and
A plurality of the semiconductor substrates are treated by repeatedly performing the process of putting the semiconductor substrate into a mixed solution of sulfuric acid and hydrogen peroxide solution and cleaning the resist to peel off the resist.
First, the mixed solution was produced, and then the mixed solution was replenished with the hydrogen peroxide solution a plurality of times.
The interval from the first generation of the mixed solution to the first injection of the semiconductor substrate into the mixed solution is defined as the standby interval (Tf), and the interval of replenishing the hydrogen peroxide solution is the replenishment interval (Ta, Assuming Tb), the method for manufacturing a semiconductor device, wherein the standby interval is equal to or less than the longest period of the replenishment intervals. The method for manufacturing a semiconductor device according to claim 1, wherein the standby interval is equal to or less than the shortest period of the replenishment intervals. The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the waiting interval and the replenishment interval are all equal periods. The method for manufacturing a semiconductor device according to any one of claims 1 to 3, wherein replenishing the hydrogen peroxide solution is performed once before peeling the resist from each of the semiconductor substrates. The interval from replenishing the mixed solution with the hydrogen peroxide solution to charging the semiconductor substrate into the mixed solution is defined in any one of claims 1 to 4, which is a period shorter than the waiting interval. Manufacturing method of semiconductor devices. When the hydrogen peroxide solution is replenished from the second time onward, the interval between replenishing the mixed solution with the hydrogen peroxide solution and adding the semiconductor substrate to the mixed solution is equal to or longer than the standby interval. The method for manufacturing a semiconductor device according to any one of claims 1 to 4, wherein the hydrogen peroxide solution is replenished in an amount larger than the amount when the hydrogen peroxide solution is replenished for the first time. By replenishing the mixed solution with the hydrogen peroxide solution, the temperature of the mixed solution is measured, and when the temperature of the mixed solution becomes equal to or higher than a predetermined threshold temperature, the replenishment of the hydrogen peroxide solution is stopped. The method for manufacturing a semiconductor device according to any one of claims 1 to 6. By replenishing the mixed solution with the hydrogen peroxide solution, the temperature of the mixed solution is measured, and even if the hydrogen peroxide solution is replenished with a predetermined threshold replenishment amount, the temperature of the mixed solution is the predetermined threshold temperature. The method for manufacturing a semiconductor device according to any one of claims 1 to 7, wherein when the temperature is less than the above, the mixed liquid is discarded.

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