TW444519B - Method for reducing plasma damage - Google Patents

Abstract

A method for reducing a plasma damage caused by a metal etching machine comprises providing an inductively coupled plasma reactor, which at least comprises a top power; mounting a substrate having a semiconductor structure in the inductively coupled plasma reactor, the semiconductor structure at least comprising a metal layer and a photoresist layer; performing a major etching step to remove most of the metal layer that is not protected by the photoresist layer; turning off the top power of the inductively coupled plasma reactor; performing an over etching step to remove the metal layer remained from the major etching step, thereby avoiding the existence of a large difference in electric potential damaging the semiconductor structure to reach a conduction equilibrium.

Description

4445 1 9 V. Description of the invention (1) ------ 5-1 Field of invention: The main purpose of the present invention is to adjust the recipe of the inductively coupled plasma etching machine (ICP). In the present invention, the inductive coupling type electro-polymer etching machine (UCP) is used to shut off the induction supply (Top power) during the over-etching step (oveve step), thereby avoiding the occurrence of the over-etching step. Unstable plasma, thereby reducing the occurrence of plasma damage. 05-2 Background of the Invention: As components become smaller and smaller (<〇_25 / ζηι), and wafer sizes become larger and larger (&gt; 8 inches), Syria The selectivity and uniformity of the pattern become very important. Traditional active ion reactors (RIE) have high operating pressures and will no longer be applicable. They are replaced by high plasma density plasma systems. Such plasma systems can not only generate high density plasmas at extremely low pressures, but also Control plasma density and ion energy 'to reduce ion damage. It can also maintain good uniformity on large-size wafers and improve production yield. However, in the process of semiconductor device manufacturing, the high-frequency plasma button engraving process is often accompanied by the generation of excess ions, which will cause damage to the device. In the principle of M0S, we clearly understand that the electrical quality of the gate oxide layer has a huge impact on the M0S element. When a charge exists near the interface of Si-Si 02, it will naturally attract Opposite electricity

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The charge appears on the side of the silicon substrate, so it will affect the ideal characteristics of Mos. These charges change the turn-on voltage vt (Threshold Voltage) of the ON and OFF (0FF) of the M0S element, reduce the Break voltage of the M0S, and reduce the reliability of the product (ReiiabiUty). The charges generated in the oxide layer are mainly: 1. The interface is trapped in the charge (

Interface Trapped Charge); 2_ Fixed oxide charge (

(Fixed Oxide Charge); 3_ Mobile ionic charge; / Oxide Trapped Charge. Among them, the above-mentioned oxide layer charge has no specific distribution position, mainly due to other processes in the wafer manufacturing process, such as ion implantation, plasma etching, and electrons and holes caused by physical vapor deposition. The damage caused by plasma is being studied enthusiastically, which is called Plasma Charging Damages, or antenna effect

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Should (Antenna Effect). The area ratio or side length ratio between the conductor and the gate oxide layer is the Antenna Ratio. Generally speaking, the larger the antenna ratio, the more serious the damage. This is because the antenna ratio is larger. The more charge the body collects, the more electricity is applied to the gate oxide layer. In addition, the longer the time of over-etching, the more serious the damage is, because the longer the time that the current passes through the gate oxide layer, the more defects are generated. The antenna effect can be divided into two types according to different processes. One is area effect, such as photoresist ashing. When the photoresist is removed ’, the t-charge is collected by the surface of the conductor, so the larger the conductor area is

Page 5 4445 1 9 V. Description of the invention (3) The more charge collected, it is called area effect. The other is the side length effect, such as silicon and aluminum etching. At this time, the surface of the conductor is covered by photoresist and is not affected by the accumulation of charge. However, when the etching is near the end, some conductors are too thin and cause resistance. If the value is too high, excess charge will be transferred to the Shixi substrate through the gate oxide layer. In addition, charge may accumulate on the gate oxide through the side walls of the conductor. These damages become more serious as the length of the conductor side becomes longer, which is called side effect. In addition, in the development of integrated circuits, the gate oxide layer is becoming thinner and thinner, and it is more and more sensitive to Plasma Damage (

Sensitive), one of the main sources of electrical damage caused by metal etchers (Metal Etcher) in the process. The current metal etcher can be divided into: (1) magnetic field enhanced active ion etchers (Magnetic-Enhanced Reactive I on Etcher, MERIE for short) (2) Electron cyclotron resonance is a plasma etching machine (Electron Cyclotron

Resonsnce Plasma Etchers (ECR) (3) Inductively Coupled Plasma Reactor (ICP) and other systems. In the field-enhanced active ion etching machine (jjer IE) system, the magnetic field is generally turned off to avoid the occurrence of plasma damage. In addition, in the method of using an inductively coupled plasma etching machine (ICP), plasma damage can be reduced by increasing the etching pressure or reducing the power supply during etching. Due to the uneven local charge in the plasma, the charge is accumulated in a very large area.

4445 1 9 V. Description of the invention (4) On a large or long conductor (such as polycrystalline silicon, aluminum alloy), these charges will generate an electric field on the thin gate oxide layer. When enough charge is collected, the electric field across the interrogated oxide layer will cause a current to pass through the gate oxide layer, causing damage. Moreover, this damage usually occurs during over-etching, because the conductors are still continuous before the etching is completed, and the locally uneven charges will neutralize each other, and finally they can maintain electrical neutrality. After the etching is completed, the conductors are no longer connected, and uneven charges will continue to accumulate during over-etching, eventually causing damage to the gate oxide layer. Therefore, better design methods need to be developed to further reduce the damage of plasma. 5-3 Purpose and Summary of the Invention: In view of the above-mentioned background of the invention, many disadvantages that still occur during the traditional use of metal etching mechanisms need to be further improved. The main purpose of the present invention is to change the inductively coupled plasma etching machine ( ICP) programming. Generally, the metal Etcher programming includes two parts: a main etching step and an over-Etch step. The present invention uses an inductively coupled plasma etching machine (ICP). ) When the Over-Etch step is performed, the top power is turned off, thereby avoiding the generation of unstable plasma in the over-etch step, thereby reducing the occurrence of plasma damage. According to the above object, the present invention provides a method for reducing plasma damage caused by a metal etching machine. First, provide inductive coupling

4445 1 9 5 'Explanation of invention (5) Plasma etching machine (ICP), this inductively coupled plasma etching machine has at least an upper induction supplier. Next, a substrate having a semiconductor structure is placed in the inductively coupled plasma etching machine. The semiconductor structure includes at least a metal layer and a photoresist layer, and then a main etching step is performed, and most of the photoresist layer is protected by the main etching. The metal layer is removed. Turn off the upper induction supplier of this inductive electrical etching machine, and then carry out over-etching, and remove the metal layer remaining in the main etching step to avoid a large potential difference in the crystal balance, which will damage the semiconductor structure and turn on. Explanation 5: The 4 formula is simple and easy. Let the above-mentioned and other features, features, and advantages of the invention be more detailed. For example, a preferred embodiment is described in detail. The picture shows a typical inductively coupled plasma etching machine (Icp) structure. The structure is made of metal, and the semi-conductive part of the over-etching step is the representative symbol of the main part: Upper induction supplier

Page 8 4445 1 9 V. Description of the invention (6) 1 Ob inductive supply 12 Inductive coil 14 Dielectric window 1 6 Multi-pole magnet 18 Plasma 2 0 Chip 22 Wafer holder 100 Inductive supply 102 Inductive Supplier 104 silicon substrate 106 gate oxide layer 108 polycrystalline silicon layer 110 contact window 112 metal dielectric layer 114 metal layer 116 photoresist layer 118 dam age current 120 charge group 122 accumulated charge 5-5 invention Detailed description: As shown in detail in the first figure, the cross-sectional structure of the inductively coupled plasma etching machine (ICP), as shown in the figure, the structure includes:

4445 1 9 V. Description of the invention (7) The reactors 10a and 10b, the induction supply 1 Oa on the upper side is connected to the induction coil 12 with a spiral winding, and the lower induction supply 1 Ob is connected to the wafer holder 22, and Here, the wafer holder 22 is used to place the wafer 20. Above the reactor, there will be a dielectric layer window 14, which is located below the induction coil 12, and a multi-pole magnet 16 is present on each side of the reactor. The effect of plasma will be generated below the dielectric layer window 14 ^ The position where this plasma 18 is generated is only a few average free paths from the wafer 20 on the wafer holder 22, so it can produce extremely high density Plasma. When using an inductively coupled plasma etching machine (ICP) to complete the metal etching process, the second picture will be used to explain in more detail how to adjust the program settings of this etching machine to reduce the damage of the plasma. purpose. First of all, an inductively engaged plasma money engraving machine as shown in the first figure is provided for performing a metal etching process. Next, a hard substrate 1Q4 with multiple interconnect structures is placed in an inductively coupled plasma etching machine. The multiple interconnect structures on this silicon substrate include at least a gate oxide formed on the silicon substrate 104. Layer 106, and the gate oxide layer 106 has formed a polycrystalline silicon layer 108, and a contact window 11o is used to connect the lower polycrystalline silicon layer 108 and the upper metal layer 114, and the polycrystalline silicon layer 1 Between 0 8 and the metal layer 11 4, except for the contact window 110, the inner metal dielectric layer 11 2 is filled, and the isolation effect is achieved by this insulator. In addition, a photoresist layer 116 is formed to cover Above the metal layer 114, a mask is etched as a pattern of the metal layer 114. "

Page 10 4445 1 9 V. Description of the invention (8) Start the inductively coupled plasma plasma etching machine to produce high density plasma (High Density Plasma) 'Using plasma to dissociate the etching gas to generate charged ions, molecules, electrons and reactions A very strong atomic group forms a high-energy charge group 1 2 0. This high-energy charge group 1 2 0 can be used to achieve the result of anisotropic etching of metal. Usually, the metal etching program of the inductively coupled plasma etching machine is set up, including two parts: the main etching step and the over-etching step. First, the main name-engraving step is performed to remove most of the metal layer 114 protected by the photoresist-free layer 116 by the main name-engraving step to complete the pattern metal layer 114, but in the main etching step, incident electrons may not be able to be removed. The phenomenon of charge up (Charge Up) caused by conduction, but the charge accumulation (Charge Up) generated in this step can be conducted through the connected metal film, effectively balancing the potential difference generated by the plasma. Next, the upper induction supplier 100 of this inductively coupled plasma etching machine is turned off. Because after the pattern metal layer 114 formed by the main etching step, 'the residual metal layer 114 still exists and has not been removed, it is completely removed', so an over-etching step is required to completely remove the residual metal layer 114 'but usually During the over-etching step, because the patterned metal layer Π4 is about to be formed. “When the metal layer 114 is formed, the accumulated charge 122 generated during this over-engraving step cannot be conducted through the metal thin film. When there is a large potential difference, the charge will penetrate the contact window 110 ′ and pass through the polycrystalline dream layer 108 ′ to further destroy the gate oxide layer 106 to turn on the balance ”or even generate a damage current 118

4445 1 9 Five 'invention description (9) Therefore, in a preferred embodiment of the present invention, the upper induction supplier 1 0 of this inductively coupled plasma etching machine is turned off during the over-etching step. In order to overcome the problem of plasma damage caused by the accumulated charge 1 2 2, the above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention; all others do not depart from the disclosure of the present invention Equivalent changes or modifications made under the spirit should be included in the scope of patent application described below.

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Claims (1)

\ 4445 1 9 1 A method for reducing plasma damage, the method at least comprising: providing a metal etching machine, the metal etching machine including at least an upper induction supplier; placing a substrate having a semiconductor structure in the metal etching machine A metal main etching step; closing the upper induction supplier of the metal engraving machine; and performing a metal over-buttoning step 'removing the metal remaining from the metal main etching step', thereby avoiding the over-etching The potential difference 'caused by the unstable electrical destruction in the step destroys the semiconductor structure and turns on the balance. 2. The method according to item 1 of the scope of patent application, wherein the semiconductor structure includes at least a metal layer and a photoresist layer. 3. The method as described in the scope of patent application, item 1, wherein the aforementioned metal etching machine can be an inductively coupled plasma etching machine. 4. The method described in item 1 of the stated red patent of the patent, wherein the above-mentioned main engraving step is to remove most of the metal layer of the semiconductor structure without the photoresist layer protection. 5. A method of reducing plasma damage caused by a metal etching machine, the method at least comprising: providing an inductively coupled plasma etching machine, the inductively coupled plasma Page 13 4445 1 9 VI. Application scope &quot; ----- In the etching machine, there is at least one upper induction supplier; a substrate with a semiconductor structure is placed in the inductively coupled plasma button engraving machine The semiconductor semiconductor structure includes at least a metal layer and a photoresist layer; a main etching step is performed, and the majority of the metal layer without the photoresist layer protection is removed by the main etching step; closing the inductive coupling The upper induction supplier of the plasma etching machine; A ...... performs an excessive remaining step to remove the metal layer remaining in the main etching step ^ ^ to thereby avoid the Excessive etching of Ferrocite from the potential difference caused by the unstable plasma in the 'less' step destroys the semiconductor structure and waves. 3 τ &amp; J finds the equilibrium. Page 14