TWI570803B - A deep silicon etch method - Google Patents

Description

Deep etch method

The present invention relates to the field of semiconductor fabrication, and more particularly to a deep etch method.

The etching process refers to a process of removing a unnecessary portion in a wafer or a wafer surface film layer by using a chemical solution or a corrosive gas or a plasma during the process of manufacturing a semiconductor device. Generally, the method of etching mainly with a chemical solution is wet etching, and the method of etching with a corrosive gas or plasma is dry etching. At present, dry etching, which can make circuit patterns finer, is more and more widely used.

In the wet etching, isotropic etching is performed by a chemical reaction of a strong acid, and even a portion covered by the photomask can be etched. In contrast, dry etching is performed by reactive ion etching in which etching is performed using a corrosive chemical gas such as a plasma halogen and a plasma ion. Therefore, the dry etching can realize an anisotropic etching in which the etching is performed only on the wafer in the vertical direction. Therefore, the dry etching is suitable for a fine process requiring high precision, for example, for a very large integrated circuit (VLSI) process.

A conventional plasma processing apparatus includes a reaction chamber into which a processing gas is introduced, and a parallel plate electrode composed of a pair of upper electrodes and lower electrodes is disposed in the reaction chamber. While introducing the processing gas into the reaction chamber, a high-frequency voltage is applied to the lower electrode to form a high-frequency electric field between the electrodes, and a plasma of the processing gas is formed by the high-frequency electric field.

The well-known deep hole via etching of the prior art mainly involves the fabrication of via vias or trenches. Among them, in the process of transferring the pattern from the photoresist to the hard mask, it is necessary to ensure that the pattern transferred to the hard mask is not deformed, so that sidewall etching is not performed during the etching of the hard mask. It will not eventually cause a size shift. For sufficient etch rate, deep via etching is also avoided as an isotropic etch. In the trend of higher and higher component accuracy requirements, the above two requirements can not usually be taken into account. Common problems include the presence of a curved outline on the sidewall of the etch, such that the line size of the etch and the line size defined by the reticle exhibit a large critical shift (CD shift).

Therefore, there is a need in the industry for a deep via etch mechanism that ensures etched topography while maintaining a high etch rate.

In view of the above problems in the background art, the present invention proposes a deep etch method.

The present invention provides a deep etching method, wherein the etching method comprises the following steps:

An anisotropic etching step, providing a first reactive gas to etch the layer of germanium material under the action of plasma, and etching to a depth to expose an etching interface, the etching interface comprising a sidewall, the first reactive gas comprising An etching gas and a sidewall shielding gas for compensating an etching action of the etching gas on the sidewall in a lateral direction;

a sidewall protecting step, providing a second reactive gas, forming a sidewall protective layer on the sidewall of the etching interface under the action of the plasma, adhered to the sidewall surface of the etching interface, and the second reactive gas includes a sidewall shielding gas;

The anisotropic etching step and the sidewall protecting step are alternately cycled until the etching reaches the target depth.

Further, the execution time ratio of the anisotropic etching step and the sidewall protection step is greater than 5:1.

Further, the execution time ratio of the anisotropic etching step and the sidewall protection step is greater than 5:1 and less than 20:1.

Further, the first reactive gas includes an etching gas of SF ₆ .

Further, the first reaction gas includes a sidewall shielding gas including C ₄ F ₈ , O ₂ , SiF ₄ .

Further, the ratio of the etching gas and the sidewall shielding gas in the first reaction gas is 4:1 to 2:1. .

Further, the first reaction gas includes a sidewall shielding gas including C ₄ F ₈ or O ₂ .

Further, a mask layer or a photoresist layer is further disposed on the layer of germanium material.

Further, the anisotropic etching step and the sidewall protecting step are alternately cycled until the etching reaches a target depth to form a via hole or a trench.

Further, the etching method is performed in an inductively coupled plasma etching chamber.

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Specific embodiments of the present invention will be described below with reference to the accompanying drawings.

Deep hole etch is typically performed in an inductively coupled plasma etch chamber. 1 is a schematic view showing the structure of an inductively coupled plasma processing chamber. The inductively coupled plasma processing apparatus 100 includes a metal sidewall 102 and an insulating top plate 104 that form a hermetic vacuum enclosure and is evacuated by an evacuation pump (not shown). The insulating top plate 104 is merely an example, and other top plate patterns such as a dome-shaped metal top plate with an insulating window may be used. The susceptor 106 includes an electrostatic chuck (not shown) on which the substrate W to be processed is placed. Bias power is applied to the electrostatic chuck to create a clamping force on the substrate W. The RF power of the RF power source 108 is applied to a RF power transmitting device located on the insulating top plate 104. In the embodiment, the radio frequency transmitting device includes a radio frequency coil 110. The process gas is supplied from the gas source through the line to the reaction chamber to ignite and sustain the plasma, thereby performing a deep etch process on the substrate W. Preferably, the process gas enters the chamber from the gas injection port 112.

The deep etching mechanism of the prior art generally includes two types, one of which is ordinary deep etching, that is, a non-Bosch process deep etching. 2 is a schematic view showing the morphology of a non-Bosch deep etched via/groove of the prior art. The non-Bosch deep etch is a simultaneous introduction of a reactive gas and a sidewall shielding gas to simultaneously perform etching and sidewall protection steps. Due to the simultaneous etching and sidewall protection steps, the non-Bosch deep etch etch rate is fast and there is no wavy appearance on the sidewalls of the Bosch process. However, the disadvantages of the non-Bosch deep etch are also very obvious. As shown in FIG. 2, the ruthenium substrate 204 is etched by using the mask layer 202 as a mask, and the resulting through-hole or the trench 200 is tapered. In the shape, the opening of the upper portion is larger, and the opening becomes smaller as the through hole or the vertical extension of the groove.

Another use of the deep etch mechanism of the prior art is the Bosch process. The Bosch process can switch the etching step and the sidewall protection step separately, and the etching step and the sidewall protection step are performed cyclically to achieve the etching depth. . 3 is a flow chart of a process step of etching a through hole/trench in the prior art by Bosch. As shown in FIG. 3a, an etching step is first performed, and the mask layer 302 is used as a mask to etch the germanium substrate 304. An opening 306 is obtained. Next, a sidewall protection step is performed, as shown in FIG. 3b, a sidewall protection layer 308 is deposited over the mask layer 302 and on the sidewalls of the etch interface. Then, the etching step is continued, and a deeper etching interface is formed as shown in FIG. 3c. As shown in FIG. 3c, the Bosch etching method forms a wavy topography on the sidewall of the etching interface, and finally forms a deep hole 300. Or the trenches are also wavy, and the etching efficiency is also very low.

In order to solve the above problems, the present invention proposes a deep etch method. 4a-4d are flow diagrams of process steps of a simmer etching process in accordance with an embodiment of the present invention. The deep etching method provided by the present invention is described in detail below with reference to FIGS. 4a to 4d, and includes the following steps.

As shown in FIG. 4a, an anisotropic etching step is first performed to provide a first reactive gas to etch the germanium material layer 404 under plasma and etched to a depth to expose an etch interface 406. 406 includes a sidewall 404a. Wherein, the first reactive gas comprises an etching gas and a sidewall shielding gas, the etching gas is used for etching the germanium material layer to a predetermined depth, and the sidewall shielding gas simultaneously forms a sidewall protective layer on the sidewall 404a of the etching interface 406 during the etching process. . Since the sidewall shielding gas and the etching gas act simultaneously, the sidewall protective layer on the sidewall 404a cannot be retained in this step because it is eroded by the etching effect, however, the sidewall on the sidewall 404a in this step The protective layer also neutralizes the force in the lateral direction of the etching action, taking into account the etching speed.

As shown in FIG. 4b, a sidewall protection step is then performed to provide a second reactive gas. Under the action of the plasma, a sidewall protective layer 408 is formed on the sidewall of the etched interface 406 to adhere to the surface of the sidewall 406a of the etched interface 406. Wherein, the second reaction gas comprises a sidewall shielding gas. The sidewall protection layer 408 can protect and compensate the lateral diffusion tendency of the etched interface that has been completed, and does not destroy the depth that the previous anisotropic etching step has been completed when the non-isotropic etching step is performed next. It can continue to extend downwards, so that there is no problem that the etching morphology of the prior art appears to be tapered.

As shown in Figure 4c, a second anisotropic etch step is continued to provide a first reactive gas to further etch the germanium material layer 404 under the action of the plasma and etch to a deeper depth. Wherein, the first reactive gas comprises an etching gas and a sidewall shielding gas, and the etching gas is used to continue etching the germanium material layer 404 to a predetermined depth, and the sidewall protective gas continues to be simultaneously performed on the sidewall 404a of the etching interface 406 during the etching process. Sidewall protection layer. In this step, the sidewall protection layer 408 deposited by the previous sidewall protection step is simultaneously etched away, but compensates for the tendency of the etching to spread at a depth that has already been achieved. The newly formed sidewall protective layer on the sidewall 404a in this step is still responsible for neutralizing the etching force in the lateral direction of the depth etched by this step, and taking into consideration the etching speed.

As shown in FIG. 4d, the second sidewall protection step is continued to provide a second reactive gas. Under the action of the plasma, a sidewall protective layer 408' is formed on the sidewall of the etching interface 406, and is attached to the etching boundary 406. The surface of the side wall 406a. Wherein, the second reaction gas comprises a sidewall shielding gas. The anisotropic etching step and the sidewall protecting step are then alternately cycled until the etching reaches the target depth.

Further, the anisotropic etching step and the sidewall protecting step are alternately performed as described above, and the execution time ratio of both is greater than 5:1. The present invention provides more time in the anisotropic etching step, so that the etching rate can be maintained, and since the anisotropic etching step also has sidewall protection simultaneously, the through hole/矽 trench is also ensured to some extent. The shape does not produce a cone, so more time can be performed.

Preferably, the execution time ratio of the anisotropic etching step and the sidewall protection step is greater than 5:1 and less than 20:1. For example, it includes 6:1, 7.2:1, 9:1, 12:1, 13.5:1, 18:1, and the like.

Further, the first reactive gas includes an etching gas of SF ₆ .

Further, the first reaction gas includes a sidewall shielding gas including C ₄ F ₈ , O ₂ , SiF ₄ .

Further, the ratio of the etching gas and the sidewall shielding gas in the first reaction gas is 4:1 to 2:1, for example, 3.8:1, 3.2:1, 2.35:1, 2.58:1, or the like.

Further, the first reaction gas includes a sidewall shielding gas including C ₄ F ₈ or O ₂ .

Further, the enamel material layer is further provided with a photomask layer or a photoresist layer for etching the ruthenium material layer as a reticle to form a 矽 or a trench

Further, the anisotropic etching step and the sidewall protecting step are alternately cycled until the etching reaches a target depth to form a via hole or trench 400.

FIG. 5 is a schematic view showing the shape of a via/groove manufactured by a simmer etching method according to an embodiment of the present invention. As shown in FIG. 5, the through-hole/germanium trench 400 obtained by performing the squeezing etching method of the present invention has a deep depth, and the lateral widths thereof tend to be uniform from top to bottom, and the sidewalls of the prior art are not presented. The wavy or side wall presents a problem of taper. Moreover, the present invention maintains a high etching rate while taking into account the topography of the via/germ trench 400.

Although the present invention has been described in detail by the preferred embodiments thereof, it should be understood that the foregoing description should not be construed as limiting. Various modifications and alterations of the present invention will be apparent to those of ordinary skill in the art. Accordingly, the scope of the invention should be defined by the appended claims. In addition, any reference signs in the claim should not be construed as limiting the claim. The term "comprising" does not exclude the other claim or the means or steps not listed in the specification; "first", " Words such as "two" are used only to denote a name, and do not denote any particular order.

100‧‧‧Inductively coupled plasma processing unit
102‧‧‧Metal sidewall
104‧‧‧Insulated roof
106‧‧‧Base
108‧‧‧RF power supply
110‧‧‧RF coil
112‧‧‧ gas injection port
200‧‧‧矽through hole or trench
202‧‧‧mask layer
204‧‧‧矽Base
300‧‧‧Deep hole
302‧‧‧mask layer
304‧‧‧矽 substrate
306‧‧‧ openings
308‧‧‧ sidewall protection
400‧‧‧矽through hole or groove
404‧‧‧矽 material layer
404a‧‧‧ side wall
406‧‧‧ etching interface
406a‧‧‧ side wall
408, 408'‧‧‧ sidewall protection
W‧‧‧ substrates

[Fig. 1] is a schematic structural view of an inductively coupled plasma processing chamber; [Fig. 2] is a schematic view showing the morphology of a non-Bosch deep etched via/groove of the prior art; [Fig. 3a]~[Fig. 3c] A flow chart of a process step of etching a through hole/groove in the prior art by Bosch; [Fig. 4a] to [Fig. 4d] is a flow chart of a process step of a simmer etching method according to an embodiment of the present invention; 5] is a schematic view of the shape of a via/groove manufactured by a simmer etching method according to an embodiment of the present invention.

400‧‧‧矽through hole or groove

Claims (7)

A deep etching method includes the following steps: an anisotropic etching step, providing a first reactive gas to etch a layer of germanium material under the action of plasma, and etching to a certain depth to expose an etching interface, the etching interface Including a sidewall, the first reactive gas includes an etching gas and a sidewall shielding gas, and the ratio of the etching gas and the sidewall shielding gas in the first reactive gas is 4:1 to 2:1, and the sidewall shielding gas is used for compensation The etching gas etches the sidewall in the lateral direction; the sidewall protecting step provides a second reactive gas, and under the action of the plasma, a sidewall protective layer is formed on the sidewall of the etching interface, and is attached to the etching The sidewall surface of the interface, the second reactive gas includes a sidewall shielding gas; alternating the anisotropic etching step and the sidewall protecting step until the etching reaches a target depth; wherein the anisotropic etching step and The execution time ratio of the sidewall protection step is greater than 5:1 and less than 20:1. The smear etching method according to claim 1, wherein the first reaction gas includes an etching gas of SF ₆ . The smear etching method according to claim 1, wherein the first reaction gas includes a sidewall shielding gas including C ₄ F ₈ , O ₂ , SiF ₄ . The smear etching method according to claim 2, wherein the second reaction gas includes a sidewall shielding gas including C ₄ F ₈ or O ₂ . The smear etching method according to claim 1, wherein the enamel material layer is further provided with a photomask layer or a photoresist layer. The smear etching method of claim 1, wherein the anisotropic etching step and the sidewall protecting step are alternately cycled until the etching reaches a target depth to form a via hole or a trench. The smear etching method of claim 1, wherein the simmering etching method is performed in an inductively coupled plasma etching chamber.