JP2976898B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for dry etching a material, and more particularly to a method for removing residual charges from a semiconductor wafer in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In recent years, high integration of semiconductor devices has progressed, and with the miniaturization of patterns, the importance of dry etching technology has become more and more important. In the dry etching process, controlling the wafer temperature during dry etching has become one of the important technologies in order to maintain the accuracy and uniformity of the pattern size.

As described above, as a method of controlling the wafer temperature, a method of fixing a wafer to a wafer stage and cooling the wafer stage by a cooling medium is generally used. As a method for fixing the wafer to the wafer stage, there are a method by electrostatic attraction and a method by which the outer peripheral portion of the wafer is pressed by a wafer press to bring the wafer into close contact with the wafer stage. Of these, a triode-type plasma etching apparatus characterized by including an intermediate electrode in addition to an upper electrode and a lower electrode generally adopts the latter wafer holding method.

FIG. 1 shows a schematic structure of a triode type plasma etching apparatus employing a wafer holding system. The triode type plasma etching apparatus A generally includes an etching chamber 1, a plasma control system 3, and a processing gas introduction system 5. A feature of the triode type plasma etching apparatus is that an intermediate electrode 17 is provided in the etching chamber 1 in addition to the upper electrode 11 and the lower electrode 15.

On the lower electrode 15, a semiconductor wafer 19 is mounted on a wafer table 21, and is fixed to the etching chamber 1 by a wafer holder 23. Further, the etching chamber 1 is provided with lift pins 25 for lifting the wafer 19 and transporting it to the next processing apparatus as shown in the figure. On the other hand, the plasma control system 3
Comprises a high-frequency power supply 31 and three controllable capacitors 33a, 33b, 33c shown in the figure.

The processing gas introduction system 5 has gas introduction pipes 35, 35, 35 for introducing a processing gas into the etching chamber 1.
, Solenoid valves 37, 37, 37, flow meters 41, 4
1 and 41, and a vacuum pump (not shown) for exhausting the etching chamber 1 is provided.

In such a triode type plasma etching apparatus A, the distance between the upper electrode 11 and the intermediate electrode 17 and the distance between the intermediate electrode 17 and the lower electrode 15 are different from those of a conventional two-electrode dry etching apparatus. Since plasma discharge can be performed and high-density plasma can be generated, there is an advantage that etching processing efficiency is high. Here, a large number of through holes 17a are provided in the intermediate electrode 17, so that the processing gas can move freely.

Here, the lower electrode 15 also serves as a wafer stage for mounting the wafer 19, and supports the wafer 19 together with the wafer table 21 from below. In addition, water is flowing through the lower electrode 15 as a cooling medium to keep the temperature of the wafer 19 constant. When unloading the wafer 19 from the etching chamber 1, the wafer table 21
Is lowered, the lift pins 25 rise, and the wafer 1
9 is lifted. Here, as a material of the wafer holder 23, an insulator such as ceramics is generally used. However, such an insulator has a problem that charges are likely to remain on the wafer 17 after plasma etching. .

Due to the influence of the residual charges, the wafer 19 comes into close contact with the wafer retainer 23 after the etching is completed. This caused a transport error. Several methods have been proposed to solve such problems.

For example, in Japanese Patent Application Laid-Open No. Hei 7-115085, a normal two-electrode type plasma etching apparatus is used instead of a triode type plasma etching apparatus. A method is disclosed in which after performing the steps, a bias is applied to the wafer and ions are incident on the wafer to remove residual charges.

In Japanese Patent Application Laid-Open No. 5-283379, a normal plasma etching apparatus, not a triode type plasma etching apparatus, is used. A method is disclosed in which a bias to be applied is made smaller than in the step of performing, so that an electrostatic attraction force is made smaller and a transport error is prevented.

[0012]

However, in the case of the wafer fixing method using the wafer holder 23, the wafer 17
As for the method for removing the residual charge, no solution has been proposed so far. Further, even if the above-described conventional technique (in the case of electrostatic attraction) is applied as it is to a dry etching technique by a triode type plasma etching apparatus using fixing means by the wafer holder 23, the wafer 17 may be damaged or unscheduled. There is a problem that the progress of etching occurs. This is because a bias is applied to the wafer 17 for several seconds to several tens of seconds.

In view of the above problems, in the dry etching method of the present invention, in the dry etching method using the triode type plasma etching apparatus, the wafer etching is performed while taking into account the mechanism peculiar to the triode type plasma etching apparatus. An object of the present invention is to provide a dry etching method in which charges remaining on a wafer after etching are quickly removed without adversely affecting the wafer, and a transport error does not occur. It is another object of the present invention to provide such a means so that in the semiconductor manufacturing process, the transfer to the next process can be performed smoothly, and that the manufacturing cost can be reduced by eliminating breakage of the wafer. .

[0014]

Means for Solving the Problems To solve the above problems, the dry etching apparatus of the present invention employs the following means. That is, in the dry etching method according to the first aspect, the upper electrode and the through-hole are many.
Also serves as a wafer stage with a number of plate-like intermediate electrodes
A lower electrode that includes three electrodes, and these upper electrode
Plasma between the intermediate electrode and between the intermediate and lower electrodes
Was discharged, a dry etching method using a triode-type plasma etching apparatus for generating a high density plasma, said dry etching method, disposed in etching chamber of the etching apparatus, on the wafer stage A first step of disposing a wafer, a second step of fixing an outer peripheral portion of the wafer in close contact with the wafer stage by a wafer holder made of a dielectric material, and A third process of performing a predetermined plasma etching by performing a discharge between the upper electrode and the intermediate electrode and between the intermediate electrode and the lower electrode using a first processing gas for etching; And using a second processing gas for removing residual charges on the wafer while keeping the wafer in close contact with the wafer stage, By performing discharge between the upper electrode and the intermediate electrode of the serial etching apparatus, and having a, a fourth step of performing a predetermined plasma etching.

In the above dry etching method,
The fourth step is added after the first, second and third steps which are usually performed. In the fourth step, plasma is generated only between the upper electrode and the intermediate electrode. Positive ions of the second processing gas in the generated plasma are attracted to the intermediate electrode, pass through the intermediate electrode, and enter the negatively charged wafer. Further, since no plasma is generated between the intermediate electrode and the lower electrode, plasma is not directly incident on the wafer disposed on the lower electrode, and no damage or the like is caused.

According to a second aspect of the present invention, in the dry etching method according to the first aspect, in the fourth step, the time for performing the plasma etching is set to a time of 1 second or more and 5 seconds or less. It is characterized by doing. In the above dry etching method, since the processing time in the fourth step is short, the wafer is not damaged, and unnecessary etching does not proceed. The above time is sufficient for static elimination.

According to a third aspect of the present invention, in the dry etching method according to the first or second aspect, a gas containing the same gas as the first processing gas is used as the second processing gas. It is characterized by using. In the above dry etching method, the first processing gas and the second processing gas are the same. Therefore, between the third step and the fourth step, the step of exhausting the first processing gas and the step of introducing the second processing gas into the processing chamber to adjust the gas pressure. The fourth step can be performed by skipping the step.

According to a fourth aspect of the present invention, in the dry etching method of the first or second aspect, oxygen, nitrogen, or an inert gas is used as the second processing gas. In such a dry etching method, when there is a situation where the first processing gas and the second processing gas cannot be the same gas, oxygen or oxygen, which is the simplest and easily available etching gas, is used. Nitrogen gas or an inert gas that does not easily react with the wafer is used.

According to a fifth aspect of the present invention, in the dry etching method according to the third aspect, the third step is performed by only stopping the discharge between the intermediate electrode and the lower electrode. Then, the process proceeds to the fourth step. In such a dry etching method, it is possible to shift from the third step to the fourth step only by stopping the discharge between the intermediate electrode and the lower electrode. In addition, the etching process can be rapidly performed.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a dry-ode type plasma etching apparatus for explaining a dry etching method of the present invention, which is completely the same as the structure shown in the conventional example and is used in common. Also, the schematic configuration of the triode type plasma etching apparatus A has been described in the conventional example, and the description is omitted.

Here, an aluminum plate having a thickness of 5 mm is used for the intermediate electrode 17, and the intermediate electrode 17 is disposed above and below the intermediate electrode 17 so that the processing gas can move.
Are provided with a large number of through holes 17a having a diameter of 4 mm over the entire surface. The wafer holder 23 is made of an insulating ceramic material.

Next, the steps of the dry etching method of the present invention will be described with reference to FIGS. First, in the first step, the Si wafer 19 is arranged on the lower electrode 15 and the wafer table 21 arranged in the etching processing chamber 1 of the etching apparatus A. A polysilicon film in which As is diffused is deposited on the Si wafer 19, and the polysilicon film is etched using a photoresist or the like as an etching mask.

Next, in the second step, the wafer table 21
At the same time, the outer periphery of the wafer 19 is pressed by the wafer holder 23 made of ceramic (dielectric material), and the wafer 19 is tightly fixed to the wafer table 21. Then, as a third step, the wafer 19 is
By performing discharge between the upper electrode 11 and the intermediate electrode 17 and between the intermediate electrode 17 and the lower electrode 15, predetermined plasma etching is performed.

Next, after evacuation by a vacuum system (not shown), SF6 gas is used as a first processing gas in the etching chamber 1 at 10 SCCM, Cl2 at 5 SCCM, and CHF3 at 5 SCCM.
It is introduced into the etching chamber 1 at a flow rate of CM. Then, the gas pressure is adjusted by a vacuum system and maintained at 200 mTorr. Here, the value of the capacitor is 33a: 33b: 33c = 2
5:15:15 is set. Then, high frequency power is set to 80 W, and normal etching is performed for 1 minute.

In this etching step, the polysilicon is etched. In this case, the wafer 19
It may be negatively charged by the influence of the plasma and may be attracted to the ceramic wafer retainer 23 (10 to 10).
At a rate of 15%, transportation is hindered). Therefore, the fourth
In the second step, the above-mentioned second processing gas, that is, O2
Is introduced at 50 SCCM, and the gas pressure is kept at 150 mTorr.

Thereafter, the value of the capacitor is set to 33a: 33
b: 33c is set to 7: 0: 10 (33b is set to 0), the high-frequency power is set to 50 W, and applied for 1 second. As a result, the residual charges on the wafer 19 are neutralized, and the wafer 1
9 does not adhere to the wafer holder 23. Next, a mechanism capable of removing the residual charge of the negatively charged wafer 19 in the above-described process will be described in detail.

FIG. 2 shows the third step. In the third step, a discharge occurs between the upper electrode 11 and the intermediate electrode 17 and between the intermediate electrode 17 and the lower electrode 15, and the positive ions in the plasma are generated when the high-frequency power (applied voltage) is negative.
Attracted by the upper electrode 11 and the lower electrode 15,
The electrons are attracted to the upper electrode 11 and the lower electrode 15 when the high frequency power is positive.

Here, since the mass of electrons is smaller than that of positive ions, more electrons are transferred to the upper electrode 11 and the lower electrode 1.
The wafer 19 attracted to the lower electrode 5 and grounded on the lower electrode 15 carries a negative charge.

FIG. 3 shows that the upper electrode 1 is formed in the fourth step.
1 shows a state in which discharge is performed between the first electrode and the intermediate electrode 17 to generate plasma. Next, the first processing gas is exhausted before moving to the fourth step. Next, in the fourth step, first, a second processing gas is introduced,
3b is set to 0.

Then, when high-frequency power is applied for 1 to 5 seconds, the second power is applied only between the upper electrode 11 and the intermediate electrode 17.
A plasma of the processing gas is generated. The lower electrode 15 always has a negative potential with respect to the intermediate electrode 17 until static elimination of the residual charge is completed.

On the other hand, the upper electrode 11 repeats positive and negative with high frequency power. Positive ions in the plasma are attracted to the intermediate electrode 17 when the high-frequency power is positive as shown in FIG. 3, pass through the through hole 17a of the intermediate electrode 17, are accelerated by a potential difference from the lower electrode 17, and are accelerated by the wafer. It is incident on 19.

On the other hand, when the high-frequency power is negative, the electrons are attracted to the intermediate electrode 17 and pass through the through-hole 17a, and then repelled by the negative potential of the lower electrode 17 and the negative charge of the wafer. Attracted to 17. As a result, the residual charges on the wafer 19 are neutralized, and as the neutralization proceeds, the incident energy of the ions decreases,
Finally, static elimination is completed. The residual charge on the wafer 19 is removed by the above mechanism.

Here, since no bias is applied directly to the wafer 19, the processing time is as short as 5 seconds or less, so that there is no adverse effect on the wafer. Thereby, the wafer 1
9 is neutralized, and the wafer 19 and the wafer holder 2 are neutralized.
The electrostatic attraction force with the wafer 3 is weakened, and the subsequent transfer process of the wafer 19 is not hindered.

The reason why the etching time by the second processing gas is set to 1 to 5 seconds is that if the etching time is 1 second or less, there is not much effect of static elimination, which may hinder the next transporting step. If the processing is performed for 5 seconds or more, there is a problem that unnecessary damage is caused to the wafer 19 or unplanned etching proceeds, and the original purpose of the charge removal is achieved within 5 seconds. Because.

As the second processing gas, oxygen gas is used here. However, nitrogen gas may be used, and if an inert gas such as argon or helium is used, etching hardly occurs.

Next, a second embodiment using the dry etching method of the present invention will be described. Here, in the fourth step, unlike the case shown in the first embodiment, a gas containing the same gas as the first processing gas is used as the second processing gas.

That is, SF6 gas is used as the second processing gas in the same manner as in the third step, that is, 10 SCCM and CSC.
A flow rate of l2 gas and a flow rate of CHF3 gas of 5 SCCM and 5 SCCM are introduced into the etching chamber 1. Then, the gas is exhausted in a vacuum system and the gas pressure is maintained at 200 mTorr. Here, the capacitors 33a: 33b: 33c are changed to 7: 0: 10, the high-frequency power is reduced to 30 W, and the etching is performed for one second.

By this etching step, the residual charge generated in the third step can be removed only by changing the capacitor and the high-frequency power without changing the second processing gas from the first processing gas. .

In this embodiment, since the same type of gas as the first processing gas is used as the second processing gas, it seems that the polysilicon on the wafer 19 may be etched. However, in the fourth step,
Etching does not proceed because plasma is generated only between the upper electrode 11 and the intermediate electrode 17, the high-frequency power is reduced, and the etching (plasma generation) time is as short as 1 second.

Next, a third embodiment of the present invention will be described. In this case, in the dry etching method described in the second embodiment, the operation shifts from the third step to the fourth step only by stopping the discharge between the intermediate electrode 17 and the lower electrode 15. I do.

In such an operation, after the etching time of the third step is completed, only the value of the capacitor is instantaneously changed without changing the gas pressure or the high-frequency power, and then the etching for one second is performed. This can be achieved by continuing. Therefore, in this dry etching method, the residual charges on the wafer 19 can be instantaneously eliminated.

[0042]

As described above, in the dry etching method according to the first aspect, a new mechanism is required to remove the residual charge of the wafer generated when performing dry etching using a triode type plasma etching apparatus. It is possible to eliminate static electricity quickly and easily.

Accordingly, it is possible to prevent a situation in which a wafer is damaged or a process line is stopped due to a transport error at the time of transport to the next process, and a reduction in manufacturing cost and a reduction in manufacturing steps can be promoted.

Next, in the dry etching method according to the second aspect, since the time of the second plasma treatment for removing the residual charges is set to 1 to 5 seconds, it is sufficient from the viewpoint of removing the charge from the wafer. And there is no unnecessary etching or damage.

In the dry etching method according to the third aspect, since the first processing gas and the second processing gas are the same gas, the transition from the third step to the fourth step becomes smooth. .

In the dry etching method according to the fourth aspect, since oxygen, nitrogen, or an inert gas is used as the second processing gas, the etching does not easily proceed, and is most commonly used. Since this is a gas, there is usually an advantage that no additional mechanism is required.

In the dry etching method according to the fifth aspect, in the dry etching method according to the third aspect, the transition from the third step to the fourth step only stops the discharge of the intermediate electrode and the lower electrode. In this step, no additional mechanism is required, and a smooth transition is possible.

As described above, according to the dry etching method of the present invention, in the dry etching method using the triode type plasma etching apparatus, the residual charge of the etched wafer, which has conventionally been a problem, can be smoothly reduced. It has become possible to remove it.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a triode type plasma etching apparatus.

FIG. 2 is a principle diagram showing a third step for explaining the principle of the dry etching method of the present invention.

FIG. 3 is a principle diagram showing a fourth step for explaining the principle of the dry etching method of the present invention.

[Explanation of symbols]

A: triode type plasma etching apparatus, 1: etching chamber, 3: plasma control system, 5: processing gas introduction system,
11 upper electrode, 15 lower electrode, 17 intermediate electrode, 1
7a: Through-hole, 19: Wafer, 21: Wafer stand, 23:
Wafer retainer, 25 lift pins, 33a capacitor, 33b capacitor, 33c capacitor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-188305 (JP, A) JP-A-6-216088 (JP, A) JP-A 8-279486 (JP, A) JP-A-7- 29879 (JP, A) JP-A-6-177092 (JP, A) JP-A-7-115085 (JP, A) JP-A-4-132219 (JP, A) JP-A-7-111259 (JP, A) JP-A-7-153740 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/3065 H01L 21/68

Claims (5)

(57) [Claims] 1. A plate provided with an upper electrode and a large number of through holes
And Jo intermediate electrode, a lower electrode also serving as a wafer stage, comprises three electrodes, of the upper electrode and the intermediate electrode
Between the electrodes and between the intermediate and lower electrodes.
A dry etching method using a triode type plasma etching apparatus for generating high-density plasma , wherein the dry etching method is disposed in an etching processing chamber of the etching apparatus.
A first step of disposing a wafer on the wafer stage; a second step of fixing an outer peripheral portion of the wafer in close contact with the wafer stage by a wafer retainer made of a dielectric material; On the other hand, by performing discharge between the upper electrode and the intermediate electrode and between the intermediate electrode and the lower electrode using a first processing gas for etching the wafer, predetermined plasma etching is performed. A third step of performing the following, while keeping the wafer in close contact with the wafer stage,
A fourth step of performing a predetermined plasma etching by performing discharge between the upper electrode and the intermediate electrode of the etching apparatus by using a second processing gas for removing the residual charge of the wafer; And a dry etching method comprising: 2. The dry etching method according to claim 1, wherein, in the fourth step, the time for performing the plasma etching is 1 second or more and 5 seconds or less. . 3. The dry etching method according to claim 1, wherein the second processing gas is the first processing gas.
A dry etching method using a gas containing the same gas as the processing gas. 4. The dry etching method according to claim 1, wherein oxygen, nitrogen, or an inert gas is used as the second processing gas. 5. The dry etching method according to claim 3, wherein the step is shifted from the third step to the fourth step only by stopping the discharge between the intermediate electrode and the lower electrode. A dry etching method characterized in that: