JPS62216332A - Plasma ashing apparatus - Google Patents

Abstract

PURPOSE:To reduce the damage to a wafer during ashing by controlling the density of a plasma by an electromagnet. CONSTITUTION:When O2 gas is introduced into an ashing unit to emit a microwave through a microwave transmitting window to gas, an O2 plasma is generated. An electromagnet 18 is deenergized to pass the plasma 19 to arrive at a wafer to ash a resist 16. This has the same strong ashing force as a barrel type plasma ashing apparatus to remove a modified layer feasibly generated at the resist after ion implanting. When the modified layer is removed by ashing to allow the normal resist to remain, the plasma cannot pass by the magnetic force when the electromagnet 18 is energized so that active particles merely arrive at the wafer 17 to ash the resist 16. This is the same as a down-flow type ashing apparatus, and the ashing with the active particles less damages the wafer than the O2 plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention is an apparatus that reduces damage to a wafer during ashing by controlling plasma density using an electromagnet.

[Industrial application field]

The present invention relates to a plasma ashing device, and more specifically, to an ashing device that can serve as two different types of ashing means.

(Prior Art) Microfabrication in semiconductor integrated circuits and the like is performed by etching underlying insulating films, semiconductor films, and metal films through a resist film in which a pattern is formed by exposure and phenomena.Microfabrication, That is, after etching is completed, the resist film used as a mask must be removed from the wafer surface.

In conventional wet processing using liquid chemicals (see Figure 4), hot concentrated sulfuric acid, hydrogen peroxide, organic solvents, hot organic acids, etc. have been used, appropriately selected depending on the underlying material. However, these liquid chemicals used in the wet resist removal process are far from clean and contain various impurities, which can cause pattern defects and become a source of contamination. This is a major obstacle in improving the level of microfabrication. In addition, a large amount of chemicals are used, and the work is completely manual and inefficient, so it is not an economical method. Furthermore, many of the chemicals used in this process are harmful to the human body, and there are problems in terms of work safety and pollution prevention for waste liquid treatment, so it was necessary to change the treatment method using liquid chemicals.

Therefore, in recent years, the resist removal method of ashing (ashing) the resist using 02 plasma has pioneered the wafer processing technology using gas plasma.
Plasma ashing eliminates the above-mentioned disadvantages of wet processing and technical problems of fixation, and simplifies, cleans, and stabilizes the process, and at the same time facilitates automation.

For example, the principle of ashing a resist film using 02 plasma is that the polymer resin is reduced in molecular weight by a chemical reaction between atomic oxygen O generated in the 02 plasma and the polymer resin, and CO is oxidized by the low molecular resin.

It uses the decomposition and vaporization action to form C, H, +
It is thought to be based on the reaction O-4Cot + H2O.

Generally, such resist removal is called ashing, but in reality it is equivalent to vaporizing the resist.

As described above, since the plasma process is cleaner than the wet process, it contributes to improving the yield and reliability of integrated circuits having finely processed evaporation.

On the other hand, as miniaturization progresses, it becomes necessary not only to remove the resist but also to use a dry etching process.As a result, when the resist film is used as an etching mask, it is exposed to plasma irradiation with an etching gas or ion beam for etching. receive irradiation. Furthermore, it is becoming more common to use ion implantation to locally introduce impurities into the wafer surface using a resist film as a mask, and at this time, the resist film used as a mask is also exposed to the ion beam. The resist film subjected to such irradiation is
It is often experienced that a deterioration layer develops that cannot be removed satisfactorily with conventional liquid chemicals (see Figure 5).

From this point of view, the ashing chamber stage for resist films using gas plasma has become an indispensable manufacturing technology in the miniaturization process.

[Problem that the invention seeks to solve]

Therefore, as shown in FIGS. 2 and 3, conventional plasma ashing devices include a down flow type ashing device and a barrel type ashing device.

In the barrel-type ashing apparatus, as shown in FIG.
Expose inside and ash. Although this apparatus can remove the altered layer 42 (see FIG. 5) formed on the surface of the resist 36 described above, there is a problem in that since the wafer 38 is exposed to the plasma 39, the damage is large and the characteristics of the integrated circuit etc. are deteriorated.

Further, as an example of the down flow type ashing device, as shown in FIG. 3, the inside of the chamber 33 is divided into a plasma emission chamber 40 and an ashing chamber 43. The resist and the like on the wafer 38 are removed. Ashing using this device does not expose the wafer to plasma, so there is little damage to the wafer, but there is a problem in that it cannot remove the altered quality 1i42 formed on the resist surface due to ion implantation of high concentration impurities.

The present invention was created in view of these points, and an object of the present invention is to provide an ashing device that combines the advantages of both a down flow type ashing device and a barrel type ashing device in one device.

[Means for solving problems]

In order to achieve the above object, the plasma ashing device of the present invention has a microwave generator 11 as shown in FIG.
, a plasma 19 generator comprising an ashing gas 12, a chamber 13 containing the gas, a microwave transmission window 15 for introducing microwaves 14 into the chamber, and the microwave transmission window 15 and the resist 1 to be removed.
An electromagnet 18 is provided around the chamber 13 between the wafer 17 and the wafer 17.

[Effect]

As described above, since the ashing apparatus of the present invention is equipped with an electromagnet around the chamber 13 between the microwave transmission window 15 and the wafer 17 having the resist lines 6 to be removed,
Plasma density can be easily controlled by simply adjusting the strength of the magnet, and a single device can perform the same functions as a down flow type ashing device or a barrel type ashing device.

〔Example〕

The present invention will be explained in detail below with reference to the drawings.

FIGS. 1(a) and 1(b) show cross-sectional views of an embodiment of the present invention. FIG.
) is the state in which an electromagnet is inserted.

As shown in FIG. 1, the plasma ashing apparatus of this embodiment includes a microwave generator 11, an ashing gas 1,
2. A plasma 19 generator comprising a chamber 13 into which the gas is introduced, a microwave transmission window 15 through which microwaves 14 are introduced into the chamber, and a wafer 17 having the microwave transmission window 15 and the resist 16 to be removed. An electromagnet 18 is provided around the chamber 13 between the two.

Various types of devices can be used as the plasma ashing device described above, but in this example, a device that generates 02 plasma is used. Gas 12 is drawn into chamber 13 and microwave 15 is irradiated onto gas 12 through microwave transmission window 15, thereby generating 0□ plasma 19.

The above-mentioned wafer 17 having the resist 16 to be removed means that, for example, during the manufacturing process of semiconductors, a resist is formed on the wafer, and after performing etching, impurity ion implantation, etc., unnecessary resist is removed. Say a wafer with.

The electromagnet 18 can control the flow of plasma by its magnetic force. In this example, the first
As shown in the figure, an electromagnet 18 was provided around the chamber 13 located approximately midway between the microwave transmission window 15 and the wafer 17 having the resist 16 to be removed.

By turning off the electricity to the electromagnet 18, the electromagnet loses its magnetic force and allows the flow of plasma 19 to pass through it, and by turning on the electricity to the electromagnet 18, the plasma 19 is transferred to the electromagnet 1 by its magnetic force.
The structure is such that the plasma 19 is collected around 8 and blocks the flow of the plasma 19. In this way, the flow of plasma can be easily controlled.

Therefore, an example of ashing a resist on a wafer using the plasma ashing apparatus of this embodiment will be described.

When Oz gas is drawn into the ashing device and the gas is irradiated with microwaves through a microwave transmission window, O2 plasma is generated. As shown in FIG. 1(a), by turning off the electromagnet 18, the O2 plasma 19 passes through and reaches the wafer, ashing the resist 16.

This is the same as a barrel type plasma ashing device.

This ashing material is strong and can remove even the deteriorated layer that tends to form on the resist after ion implantation.

When the above-mentioned deteriorated layer is removed by ashing and only the normal resist remains, when the electromagnet 18 is energized, the result becomes as shown in FIG. 3(b). In this case, the 0□ plasma cannot pass through due to the magnetic force, and only the active particles reach the wafer 17 and ash the resist 16.

This is the same as a down flow type ashing device.

Since this ashing using active particles causes less damage to the wafer than O2 plasma, deterioration in characteristics can be minimized.

As described above, the ashing device of the present invention can perform two stages of down flow type and barrel type ashing with one Wl. As a result, the degraded layer is first removed using a barrel-type ashing device, and then the resist is ashed by switching to the down-flow type before damaging the wafer, making it easier to perform reliable ashing with a single device. .

〔Effect of the invention〕

As mentioned above, the ashing device of the present invention can easily switch between the down flow type ashing device and the barrel type ashing device in one device, so it is possible to reliably ash resist by combining the advantages of both devices. Became.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an embodiment of the present invention. Figure (a) shows a state in which the electromagnet is turned off, Figure (b) shows a state in which the electromagnet is turned on, and Figure 2 shows a conventional barrel-type plasma ash. FIG. 3 is a sectional view of a conventional down-flow type plasma ashing device, FIG. 4 is a sectional view of a wet peeling device, and FIG. 5 is an explanatory diagram of a degraded layer of resist. In FIG. 1, 11 is a microwave generator, 12 is an ashing gas, 13 is a chamber, 14 is a microwave, 15 is a microwave transmission window, 16 is a resist, 17 is a wafer, 18 is an electromagnet, 19 is plasma.

Claims (1)

[Claims] Microwave generator (11), ashing gas (1)
2), a microwave transmission window (15) that introduces the microwave (14) into the chamber;
), an electromagnet (18) is provided around the chamber (13) between the microwave transmission window (15) and the wafer (17) coated with the resist (16). A plasma ashing device characterized by