JPH04181728A - Dry etching method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dry etching process, which is one of the steps in the production of semiconductor devices, and particularly relates to a dry etching process for improving the shape and etching speed in dry etching. It is about the method.

[Prior Art] As a method of forming a pattern on a silicon wafer of a semiconductor material, there is a method of forming a wafer with a patterned resist mask on the uppermost layer by plasma enching.

Conventionally, in order to prevent the sidewalls of a pattern formed during plasma etching from being etched (side etching), highly adhesive particles generated in the plasma are attached to the sidewalls of the pattern. This prevented etching from progressing. This conventional etching method is called anisotropic etching by forming a sidewall protective film.

Also, pattern ljI! Another conventional etching method for protecting the I-wall is a low-temperature etching method in which, in principle, no etching reaction occurs on the side wall.

: Invention or problem to be solved] In recent years, circuits have become increasingly highly integrated and dense, and the processing dimensions have become 0.5 μm or less. In the lasma enching method, particles are deposited on the side walls of a narrow and deep chamber, which significantly reduces the particle deposition efficiency. In order to compensate for this, it is necessary to increase the mixing ratio of gases with strong deposition properties (adhesive properties). This reduces the etching speed and also adheres to the inner walls of the apparatus, resulting in further contamination inside the apparatus.

Furthermore, even after the lPI wall protective film is etched, it remains on the side of the pattern, and the material of this protective film is different from the material forming the pattern, resulting in contamination problems, dust generation problems, and pattern RK corrosion problems. This is the cause of various problems such as This is a problem in that the former conventional method requires a tipping gas that is actively mixed with the etching male.

In addition, in the latter of the conventional examples mentioned above, in principle, no etching reaction occurs on the side wall, so the absolute value of the processing temperature must be quite low, although it is ideal, and it is necessary to keep the temperature constant at a low temperature. The latter must be stable in the temperature range of 200 to 2000, and many countries are choosing the latter as a practical device.

The present invention relates to a plasma etching method for forming a protective film on a side wall, and aims at increasing the etching speed.
Moreover, it is intended to eliminate various problems caused by contamination inside the device and retained MW left on the sidewalls of the pattern.

Means for Solving the Problems The present invention supplies a reaction gas that does not produce highly adhesive dissociated products or polymerized products even when turned into plasma, and removes the material itself to be etched produced by re-dissociation of the reaction products. This method is characterized in that etching is performed while the elements are attached to the sidewalls of the pattern to be formed.

U action 1 During lasma etching, the elements of the material to be etched re-dissociate and adhere to the sidewalls of the formed pattern, preventing side etching of the sidewalls of the pattern, and preventing adhesion from the sidewalls of the material to be etched. Since it is an element, it does not contaminate the material to be etched.

"Implementation example" An embodiment of the present invention will be described below with reference to the drawings.

Conventionally, it has been thought that if the etching speed is increased, the etching of the side walls of the pattern (side etching) becomes faster and the shape of the side walls of the pattern cannot be made vertical. However, the inventor discovered that increasing the etching rate makes it easier to obtain a vertical pattern on the sidewalls of the pattern.Furthermore, the inventor discovered that when the etching rate is increased significantly, the etching product itself It was confirmed that this is due to the fact that the etching material elements are re-dissociated and the efficiency with which the elements of the etched material re-adhere to the surface of the etched material increases.

Therefore, the present invention controls the shape in pattern forming by utilizing the phenomenon of particles adhering to the side wall of the pattern, and also by re-dissociation of reaction products produced by etching the adhering particles. This is an element of the material to be etched.

The basic configuration of an apparatus for implementing the present invention will be explained with reference to FIG.

1 is a vacuum transfer chamber configured airtight;
These include an atmospheric cassette chamber 2, a load chamber 3 for introducing the material to be etched (not shown) into the apparatus, a first plasma generation chamber 4 for performing plasma etching on the material to be etched (wafer), and a corrosion prevention treatment after plasma etching. A second plasma generation chamber 5 for performing post-processing, etc., and an unloading chamber 6 for taking out the processed wafer from inside the apparatus to a cassette chamber 7 in the atmosphere are provided. 3 and the first plasma generation chamber 4 for transferring the wafer between the first transfer sII1g and the first plasma generation chamber 4.
, the second plasma generation chamber 5 , and the unloading chamber 6 .

The vacuum transfer chamber 1, the load chamber 3, and the first plasma generation chamber 4
, the second plasma generation chamber 5, and the unloading chamber 6 each have an airtight structure, and a gate valve (not shown) for blocking the flow of gas is provided between each chamber.

Further, a plasma generation m
s, a discharge gas (reaction gas) introduction system, a gas exhaust system, a power supply source such as a high frequency, a wafer mounting table on which the wafer is placed,
A wafer temperature control mechanism, a light emission monitoring mechanism for monitoring the state of plasma generation, and the like are provided (none of which are shown).

The plasma generation mechanism provided in the first plasma generation chamber 4 includes a discharge means using microwave or magnetron,
Select one using radio frequency (RF) power with a high power density such as narrow parallel plate electrodes.

In principle, the reactive gas to be supplied to the first plasma generation chamber 4 is good as long as the molecules of the reactive gas do not dissociate or polymerize and adhere to the sample surface due to the plasma, but the reactive gas has low reactivity. Gases that cannot increase the etch rate are not suitable.6 Such gases are preferably gas molecules that do not contain at least carbon C, silicon Si, etc., and gases that generate a large amount of fluorine F or chlorine C1.

Further, the temperature control mechanism has good redeposition efficiency and has a shape II.
The temperature of the wafer is controlled to a predetermined temperature that is easy to control. This appropriate temperature varies depending on the etching material, the type of reaction gas, the gas pressure, the applied ion energy, etc., and these appropriate temperatures are determined in advance through experiments, actual results, etc., and are set appropriately in accordance with the plasma etching conditions.

A specific example will be explained below.

In this example, a photoresist mask is formed on a silicon wafer sample and silicon Si is etched. Although only the case where the material to be etched is Si will be explained, polycrystalline silicon (PolySi), W-TiW,
TiN, WSi 2, and AI are almost the same.

The upper layer of photoresist was formed to a thickness of about 1.5 μm and heated at 200°C.
A coated glass SOG film with a thickness of 0.1 μm is formed on this upper layer, and a patterned resist mask is formed on the uppermost layer.

Thereafter, the coated glass SOG film and the underlying resist are etched in advance to form a mask pattern.

The generation means of the first glazma generation chamber 4 is microwave power, so that radio frequency (RF) power can be applied to the wafer for ion energy control. Microwave power is 10
The high frequency applied to the sample for ion energy control was 2 MHz and O
~10W.

Incidentally, it goes without saying that the power value varies depending on whether the high frequency is 800 kHz or 13.56 MH2 or the frequency to be applied. The wafer is cooled through the wafer table, and the cooling means for the wafer table is controlled by a combination of liquid nitrogen and a heater, or a combination of a refrigerator and a heater. Use.

The former is suitable for temperature control from 150'C to 1100C, and the latter is suitable for temperature control above 150C.

The temperature of the inner wall of the vacuum chamber, except for the wafer stand, remains at room temperature during sample cooling.

SF as Si etching gas, gas, gas pressure 1
The standard setting was 0 mTorr and a wafer temperature of about -100°C, but in W etching, etching properties such as etching shape, speed, and selectivity are excellent at about -40°C.

If the temperature of the wafer is too low, a phenomenon occurs in which the adsorption efficiency of the dissociated reaction product elements of the material to be etched becomes too high.

An example of the etching results is shown in FIG.

SF6 gas pressure 10mTorr, gas flow rate 50cc/m
In, when the sample temperature is -100'C, when the RF bias power is OW, the microwave power is 300W and there is a vertical approach or a slight side etch, and the microwave power is 400W.
If the mask is made too high, the dissociated elements of the material to be etched will adhere too much, resulting in a taper that spreads to the outside of the mask.

On the other hand, when an RF bias of 5 W was applied, a nearly vertical shape was obtained with a microwave power of 400 W. This shows that as the microwave power increases, the efficiency of re-dissociation of the reaction product gas increases, causing it to re-deposit on the side surfaces. At this time,
The lower the ion energy, the higher the deposition rate relative to the etch rate, resulting in a taper that spreads toward the outside of the mask. Therefore, a straight RF that does not taper to the outside of the mask.
Bias power exists.

In the above embodiment, even in the case where the mask is tapered outward, the amount of dirt on the inner wall of the device is extremely reduced compared to the conventional method.

Next, FIG. 3 shows the dependence on the SF6 gas flow rate and microwave power when the SF6 gas pressure is 5 mTorr, the RF bias power QW, and the sample temperature is -100°C.

When the flow rate of SF6 gas is low, a vertical shape is obtained when the microwave power is low (200 W), and when the microwave power is high (4, OOW), 50 CC/li is obtained.
At a flow rate of less than n, the machining speed is low and the mask tapers outward.

In this way, microwave power, RF power, gas flow rate, etc. have a close relationship with the pattern shape.

In other words, when the gas flow rate is low, the reaction products are mixed into the plasma as a gas, and the component ratio becomes high, so the redeposition efficiency is relatively high.When the gas flow rate is high, the reaction product component ratio is low and side etch is performed. wake up Therefore, a vertical shape can only be obtained when the etching rate is at least 1 tm/lin, and no significant results can be obtained when the etching rate is low.

As described above, by performing etching, it is possible to control the shape during pattern forming.6For example, in FIG.
When F bias is OW, microwave power is 300W and 4
If you change the power to 00W periodically, you can obtain a vertical shape.

[Effects of the Invention] As described above, according to the present invention, etching can be performed on the same side as the material to be etched under conditions of high etching rate without causing foreign elements such as a sidewall protective film from etching gas components to adhere to the sidewalls of the pattern! ! Since the shape can be controlled using a protective film, the process can be carried out horizontally with less contamination. Therefore, it is effective for processing high-yield, high-precision semiconductor integrated circuit elements, and at the same time, throughput is increased and productivity is improved. Furthermore, since dirt on the wafer and inside the device can be extremely reduced, the amount of dust generated inside the device can be reduced, and reliability can be improved.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of a dry etching apparatus for carrying out the present invention, Fig. 2 is a diagram showing the microwave and RF power dependence of the etched shape of the resist mask and the underlying silicon, and Fig. 3 is a diagram showing resist FIG. 3 is a diagram showing the dependence of the mask and the etched shape of the silicon on the SF6 gas flow rate and the microwave power. 1 is a vacuum transfer chamber, 2 is a cartridge chamber, 3 is a load chamber, 4 is a first plasma generation chamber, 5 is a second plasma generation chamber, 6 is an unload chamber, 7 is a cassette chamber, and 8 is a first transfer chamber. Mechanism, 9
indicates the side of the second conveyance Tachibana.

Claims (1)

[Claims] 1) Supplying a reaction gas that does not produce highly adhesive dissociated products or polymerized products even when turned into plasma, and forming elements of the material to be etched produced by re-dissociation of the reaction products. A dry etching method characterized by performing etching while adhering to a pattern side wall. 2) Periodically change the power supply for plasma generation to increase the redissociation and reattachment efficiency during high power cycles, and to decrease the reattachment efficiency during low power cycles to increase the etching rate. 2. The etching method according to claim 1, wherein each period is set so that the etching shape is vertical. 3) The dry etching method according to claim 1, wherein a gas not containing at least carbon element is used as the reaction gas. 4) The dry etching method according to claim 1 or 2, wherein the temperature of the material to be etched is controlled so that the vertical etching reaction progresses and the efficiency of adhesion of the re-dissociated elements to the sidewalls of the pattern is increased. 5) The dry etching method according to claim 1 or 2, wherein the sample bias current is controlled to make the etched shape vertical. 6) The dry etching method according to claim 1 or 2, wherein the reaction gas flow rate is controlled to make the etched shape vertical.