JP2001319925A - Plasma etching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the uniformity in plane distribution of the etched depth, in a dry etching apparatus wherein an etching gas is spray-applied against a wafer from a jet nozzle scanning over the entire surface of the wafer to etch the entire surface of the wafer. SOLUTION: The nozzle in a standby state is placed away from a wafer and is kept in that state until the temperature of an etching gas reaches a steady state to prevent decline of the etching rate at the start of in plane etching. By setting return points of the nozzle scanning at places away from the edges of the wafer, overetching can be prevented at the edges of the wafer to improve the uniformity in plane distribution of the etched depth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus mainly used in a semiconductor device manufacturing process and a dry etching method using the above apparatus.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a dry etching technique is frequently used for fine processing of a semiconductor substrate and a wiring layer. In dry etching, for example, a plasma is generated by microwaves, and a sample is etched by ions or an excitation gas generated thereby. Therefore, damage to the semiconductor substrate due to collision of ionized particles may be a problem. On the other hand, only gas species that can be etched only by chemical action are taken out, introduced into an etching chamber by a transport pipe, and etched by spraying an etching gas onto a sample surface from a jet nozzle. For example,
As shown in FIG. 1, an etching gas 1 is jetted from a nozzle 2, and a silicon wafer 3 placed on a work holder 5 is etched.
Is etched. Since the etching at this time is limited to the vicinity immediately below the nozzle, a local etching hole 4 is formed. In order to etch a wide range of the wafer or the entire surface of the wafer, the etching is performed while changing the relative position of the nozzle and the wafer (for example, while moving the wafer).

[0003]

In the above-mentioned etching while moving the sample, before starting the etching,
When the nozzle is placed outside the sample in a standby state, there is a problem that a sample end near the nozzle is unnecessarily etched. In addition, since the sample surface is etched by relatively scanning the nozzle, there is an operation of feeding and turning the scanning pitch at the sample end. At this time, since the residence time of the nozzle becomes substantially longer, the amount of etching at the end of the sample is increased, and there is a problem that the in-plane uniformity of the etching depth is deteriorated. Furthermore, if the etching is started immediately after the generation of the plasma, the etch rate at the beginning of the etching is reduced, and the in-plane distribution of the etching depth is deteriorated. An object of the present invention is to provide means for solving the above-described problems.

[0004]

In the dry etching apparatus according to the present invention, the nozzle position in a standby state before the start of etching is arranged so as to be separated from the sample. This prevents the etching gas from the nozzle in standby from coming into contact with the sample, thereby solving the problem that the sample end is unnecessarily etched. Further, in a small-sized apparatus, it is difficult to dispose and arrange the position of the standby nozzle from the sample, and therefore, by providing a scavenger (dedicated exhaust pipe) near the work holder, the nozzle ejects from the standby nozzle. It is also possible to adopt a method in which the etching gas to be exhausted is directly exhausted from the scavenger. Further, as for the scanning of the nozzle when the entire surface of the sample is etched, a mechanism for performing the operation of turning the scanning line at the end of the sample at a position sufficiently distant from the end of the sample is adopted. As a result, overetching at the sample end is eliminated, and the in-plane uniformity of the etching depth is improved. further,
It has been found that a predetermined time is required until the etching gas temperature reaches a steady state after the nozzle is set at the standby position before the start of etching. For this reason, a method of securing a sufficient waiting time before the start of etching is adopted. As a result, a decrease in the etch rate at the beginning of the etching is eliminated, and the in-plane uniformity of the etching depth is improved. In addition, a gas ejected from the nozzle while flowing only an inert gas (eg, Ar) serving as a base gas instead of an etching main gas (eg, NF3) originally used as an etching gas flowing to the nozzle during standby. Temperature can be stabilized. After the gas temperature reaches a steady state, the amount of the base gas is reduced, and instead, the original etching main gas is supplied to start the etching. As a result, an expensive etching main gas can be saved, and unnecessary deposits generated from the etching gas can be reduced.

[0005]

Embodiments of the present invention will be described below. Embodiment 1 FIG. 2 is a schematic plan view showing one embodiment of the present invention. Before the start of the etching, the etching gas ejection nozzle 2 is arranged with a sufficient distance L (a distance at which the wafer is not etched during the standby state of the nozzle) from the wafer 3 to be processed. After flowing an etching gas (for example, a mixed gas of an etching main gas: NF3 and a base gas: Ar 2), plasma is ignited by applying a microwave. The nozzle is kept on standby until the etching gas temperature reaches the steady temperature. When the standby time is completed, the work holder 5 is moved, the nozzle is moved to the point S shown in FIG. The turning point of the scanning line is set to a sufficient distance m from the end of the wafer 3 (the distance to the nozzle position where etching does not occur).
Is a position that can be secured. When the scanning end point S is reached,
Immediately extinguish the plasma and return the nozzle to its initial standby position. By using the above mechanism and method, the etching gas from the nozzle 2 in the standby state does not come into contact with the wafer, so that the problem that the wafer end is unnecessarily etched is solved. Also, the overrun scanning of the nozzle eliminates the overetch at the wafer end,
The in-plane uniformity of the etching depth is improved.

Embodiment 2 FIG. 3 is a schematic side view showing another embodiment of the present invention.
If there is not enough space in the etching chamber,
As in 1, the nozzle position in the standby state cannot be sufficiently separated from the wafer. The present embodiment is to solve the above-mentioned problem. As shown in the figure, a scavenger 7 (exclusive exhaust pipe) is provided near the work holder 5 on which the wafer 3 is placed, thereby sucking the exhaust gas 8 ejected from the standby nozzle and discharging it to the outside of the etching chamber. . The scavenger 7 has a moving mechanism, and can be moved to a position that does not hinder scanning before the start of scanning etching. With the above-described mechanism / method, the size of the etching chamber can be reduced.

Embodiment 3 A third embodiment of the present invention will be described below. The reason that the etch rate is lowered in the early stage of etching and the in-plane uniformity of the etching depth is impaired is that the etching gas temperature does not reach a steady state until a predetermined time has elapsed after plasma ignition. I found it. For this reason, in the present invention, a method is adopted in which the nozzle is placed at a sufficient distance from the wafer, a predetermined period of time is waited after the plasma ignition, and then the etching scan is started. It is also possible to change the component ratio of the etching gas while the nozzle is waiting before the etching. Hereinafter, a description will be given with reference to FIG. 4, which shows the passage of the component gas flow rate of the etching gas over time. First, an inert base gas (Ar in this example) 10 containing no etching main gas is supplied to the nozzle in an appropriate amount (a flow rate equivalent to stabilizing the etching gas temperature for a predetermined time when an actual etching gas flows). . Then, the plasma is ignited at time a. Next, at time b when the gas temperature becomes equivalent to the temperature in the steady state due to the actual etching gas discharge, the flow rate of the inert base gas (Ar) is reduced and adjusted to the flow rate 12 during the actual etching. At the same time, an etching main gas (NF3 in this example) 11 is caused to flow through the nozzle and adjusted to a flow rate 13 at the time of actual etching. After a predetermined waiting time (a time shorter than the waiting time) has elapsed from the time c at which the switching of the flow rate is completed, the scanning etching is started at a time d. In the case where only the etching / main gas is used without using the inert base gas at the time of actual etching, the base gas flow rate may be set to zero at the time point c.

In the above embodiments, the semiconductor substrate to be processed has been described by taking silicon as an example. However, the present invention can be applied to a compound semiconductor such as GaAs or InP by appropriately selecting the type of etching gas. Further, since the etching gas ejected from the nozzle does not contain ions, it does not cause impact damage to the surface of the workpiece. For this reason,
It is most suitable for etching for removing processing strain after mechanical polishing and grinding of a semiconductor substrate.

[0009]

The effects obtained by the present invention will be described below. (1) By keeping the position of the nozzle during standby at a sufficient distance from the wafer, the etching gas from the nozzle during standby does not come into contact with the wafer, and the problem of unnecessary etching of the end of the wafer is eliminated. (2) The retreat distance of the nozzle can be shortened by sucking and exhausting the etching gas ejected from the waiting nozzle by a dedicated scavenger. This allows
The size of the etching chamber can be reduced. (3) When the entire surface is etched by scanning the nozzle, the nozzle is overrun from the end of the wafer, and the turning point is separated from the end of the wafer, so that the overetch at the end of the wafer is eliminated and the etching depth is reduced. The uniformity of the in-plane distribution is improved. (4) Before starting etching, at the standby position of the nozzle,
By waiting until the nozzle temperature reaches a steady state, the decrease in the etch rate at the beginning of etching is eliminated,
The uniformity of the in-plane distribution of the etching depth is improved. Also,
By flowing a base gas instead of the etching main gas to the nozzle during standby, it is possible to save expensive etching gas and reduce the amount of waste gas during standby.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of a conventional dry etching apparatus.

FIG. 2 is a schematic plan view showing a first embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a second embodiment of the present invention.

FIG. 4 is a graph showing a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Etching gas 2 Etching gas ejection nozzle 3 Wafer 4 Local etching hole 5 Work holder 6 Scanning locus of ejection nozzle S Scanning start point of ejection nozzle F Scanning end point of ejection nozzle 7 Scavenger 8 Waste gas from standby nozzle 10, 12 Graph curve showing base gas flow rate 11,13 Graph curve showing etching main gas flow rate

Claims (6)

[Claims] 1. A halogen compound gas or a mixed gas containing a halogen compound gas is introduced into a plasma chamber, plasma is generated by applying an AC electromagnetic field, and the generated etching gas is ejected from an ejection nozzle through a transport pipe. The plasma etching apparatus further comprises a mechanism for moving the ejection nozzle and / or the semiconductor substrate so that the ejection nozzle scans the semiconductor substrate surface and etching the semiconductor substrate surface with the ejection gas. 2. Before starting etching of the semiconductor substrate surface, the nozzle is arranged at a position where the etching gas from the ejection nozzle does not touch the semiconductor substrate to etch the semiconductor substrate, and the nozzle is placed away from the ejection nozzle after plasma ignition. 2. The plasma etching apparatus according to claim 1, wherein the ejection nozzle is kept in a standby state until the temperature of the ejected etching gas reaches a steady state. 3. The plasma etching apparatus according to claim 2, further comprising a scavenger for sucking and exhausting the etching gas ejected from the ejection nozzle in a standby state. 4. The halogen compound gas is one of sulfur hexafluoride gas, nitrogen trifluoride gas, carbon tetrafluoride gas, chlorine gas, hydrogen chloride gas, chlorine trifluoride gas, and boron trichloride gas. Wherein the gas to be mixed with the halogen compound gas is any one of inert gases such as argon, helium, xenon, or a mixed gas of these inert gases. 4. A plasma etching method using the apparatus according to 3. 5. When the gas introduced into the plasma chamber is composed of a mixed gas of a halogen compound gas and an inert gas, when the nozzle is in a standby state, only the inert gas flows into the plasma chamber to ignite the plasma. 4. The apparatus according to claim 2, wherein when the standby state is completed, a halogen compound gas is added and flowed into the plasma chamber, and after adjusting both to a predetermined mixing ratio, etching of the semiconductor substrate is started. Plasma etching method using 6. The gas according to claim 5, wherein the halogen compound gas is sulfur hexafluoride gas, nitrogen trifluoride gas, carbon tetrafluoride gas, chlorine gas, hydrogen chloride gas, chlorine trifluoride gas, boron trichloride gas. And the gas to be mixed with the halogen compound gas is any one of inert gases such as argon, helium, xenon, or a mixed gas of these inert gases. Item 6. A plasma etching method according to item 5.