A contact hole etching method

Abstract

This invention discloses a contact hole etching method, aiming to make the tilt angle of the hole wall of the etched contact hole less than 80°. The technical solution is as follows: a contact hole etching method, comprising the following steps: forming a metal layer and an interlayer film on a semiconductor substrate from bottom to top; etching a first hole position on the interlayer film and depositing a film; defining the area to be etched on the film layer at the bottom of the first hole position; using a gas containing CF4, CHF3 and AR to etch the area to be etched, removing the film layer of the area to be etched to form a contact hole, belonging to the field of semiconductor technology.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, and more specifically, relates to a contact hole etching method. Background Technology

[0002] Semiconductor integrated circuits are integrated on the same wafer, i.e., on a semiconductor substrate such as a silicon substrate. The doped regions of the devices of the integrated circuits on the wafer need to be brought out through contact holes and metal layers, and metal interconnect structures need to be formed through contact holes and metal layers.

[0003] During etching, the first hole needs to be etched first, and then a film is deposited inside the first hole. After that, the second hole is etched at the bottom of the first hole, and the etching stops at the metal layer below. This second hole is the contact hole between the upper and lower layers. Then, metal needs to be deposited to connect the circuit. In order to facilitate the deposition of metal, the tilt angle of the hole wall of the contact hole has certain requirements, which is better at around 80° or even lower.

[0004] Therefore, it is very important to ensure that the tilt angle of the etched contact hole wall meets the requirements. Summary of the Invention

[0005] The main objective of this invention is to provide a contact hole etching method that aims to make the tilt angle of the hole wall after etching less than 80°.

[0006] According to a first aspect of the present invention, a method for etching contact holes is provided, comprising the following steps:

[0007] Step 1: Form a metal layer and an interlayer film on the semiconductor substrate from bottom to top;

[0008] Step 2: Etch the first hole on the interlayer film and deposit a film;

[0009] Step 3: Define the area to be etched on the film at the bottom of the first hole;

[0010] Step 4: Use a gas containing CF4, CHF3 and AR to etch the area to be etched, remove the film layer of the area to be etched to form contact holes.

[0011] Furthermore, in step 4, the flow rate of CF4 is 30~80 sccm.

[0012] Furthermore, in step 4, the flow rate of CHF3 is 10~30 sccm.

[0013] Furthermore, in step 4, the AR flow rate is 20~80 sccm.

[0014] Furthermore, in step 4, the pressure in the etching chamber is 5~10mt.

[0015] Furthermore, the temperature of the etching chamber is 40~45℃.

[0016] Furthermore, the upper electrode power is 500~600W, and the lower electrode power is 50~80W.

[0017] Furthermore, in step 4, the etching time is 30~65s.

[0018] Further, in step 2, a SIN film is deposited, and the thickness of the film layer in the first hole is 1800~2200 Å.

[0019] One of the above-described technical solutions of the present invention has at least one of the following advantages or beneficial effects:

[0020] In this invention, a gas containing CF4, CHF3 and AR is used to etch the contact holes. CF4 is the main etching gas, while AR gas can effectively improve the uniformity of etching. The introduction of CHF3 gas in the etching chamber does not worsen the uniformity of etching, but rather improves the morphology of etching and the production of etched polymer. The uniformity can be controlled within 3%, and the tilt angle of the hole wall of the contact hole is less than 80°. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0022] Figure 1 This is a SEM image of the contact hole after it has been cut open, processed by the etching method of Embodiment 1 of the present invention. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0024] Example 1

[0025] A method for etching contact holes includes the following steps:

[0026] Step 1: Form a metal layer and an interlayer film on the semiconductor substrate from bottom to top;

[0027] Step 2: Etch the first hole on the interlayer film and deposit a SIN film. The thickness of the SIN film layer in the first hole is 1800~2200 Å.

[0028] Step 3: Define the area to be etched on the film at the bottom of the first hole;

[0029] Step 4: Use a gas containing CF4, CHF3 and AR to etch the area to be etched, remove the film layer in the area to be etched to form contact holes;

[0030] Specifically, etching is performed in an ICP etching chamber with a pressure of 5-10 mt, a temperature of 40-45°C, an upper electrode power of 500-600 W, a lower electrode power of 50-80 W, a CF4 flow rate of 30-80 sccm, a CHF3 flow rate of 10-30 sccm, an AR flow rate of 20-80 sccm, and an etching time of 30-65 s.

[0031] CF4 is the primary etching gas, while AR gas can effectively improve etching uniformity. The introduction of CHF3 gas into the etching chamber does not deteriorate the uniformity of SIN etching; on the contrary, it improves the morphology of SIN etching and the production of the etched polymer. The etching rate of SIN can be controlled between 1200 and 3500 A / min, and the uniformity can be controlled within 3%. Figure 1 The inclination angle of the contact hole wall is less than 80°.

[0032] Comparative Example 1

[0033] Similar to Example 1, except that in step 4, a gas containing CF4, CHF3, O2 and AR is used to etch the area to be etched. The flow rate of O2 is 5~20 sccm. After etching, the uniformity is 18%~21%, which is very poor. In addition, there are many polymers that are difficult to remove at the bottom of the etched contact hole.

[0034] Comparative Example 2

[0035] Similar to Example 1, except that in step 4, a gas containing CF4, CHF3, O2 and N2 is used to etch the area to be etched. The flow rate of O2 is 5~20 sccm and the flow rate of N2 is 20~80 sccm. After etching, the uniformity is 19%~26%, which is very poor. In addition, there are many polymers that are difficult to remove at the bottom of the etched contact hole.

[0036] Comparative Example 3

[0037] Similar to Example 1, except that in step 4, a gas containing CHF3, O2, N2 and AR is used to etch the area to be etched. The flow rate of O2 is 5~20 sccm and the flow rate of N2 is 20~80 sccm. After etching, the uniformity is greater than 27%, which is very poor.

[0038] Comparative Example 4

[0039] Similar to Example 1, except that in step 4, a gas containing CHF3, N2 and AR is used to etch the area to be etched. The flow rate of N2 is 20~80 sccm. After etching, the uniformity is greater than 25%, which is very poor.

[0040] As can be seen from the examples and comparative examples, adding O2, replacing other inert gases, and lacking CF4 will all worsen the uniformity and even leave a lot of polymer residue, which will greatly affect the morphology of the pores and is not conducive to the coating.

[0041] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for etching contact holes, characterized in that, Includes the following steps: Step 1: Form a metal layer and an interlayer film on the semiconductor substrate from bottom to top; Step 2: Etch the first hole on the interlayer film and deposit a film; Step 3: Define the area to be etched on the film at the bottom of the first hole; Step 4: Use a gas containing CF4, CHF3 and AR to etch the area to be etched, remove the film layer of the area to be etched to form contact holes.

2. The contact hole etching method according to claim 1, characterized in that, In step 4, the flow rate of CF4 is 30~80 sccm.

3. The contact hole etching method according to claim 2, characterized in that, In step 4, the flow rate of CHF3 is 10~30 sccm.

4. The contact hole etching method according to claim 3, characterized in that, In step 4, the AR flow rate is 20~80 sccm.

5. The contact hole etching method according to claim 1, characterized in that, In step 4, the pressure in the etching chamber is 5~10mt.

6. The contact hole etching method according to claim 1, characterized in that, In step 4, the temperature of the etching chamber is 40~45℃.

7. The contact hole etching method according to claim 1, characterized in that, In step 4, the power of the upper electrode is 500~600W, and the power of the lower electrode is 50~80W.

8. The contact hole etching method according to claim 1, characterized in that, In step 4, the etching time is 30~65s.

9. The contact hole etching method according to claim 1, characterized in that, In step 2, a SIN film is deposited, and the thickness of the film layer in the first hole is 1800~2200 Å.

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