JPS63215080A - Nonvolatile semiconductor memory and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent movable ions from penetrating through a contact hole by a method wherein a film hardly passing movable ions is formed in the sidewall part of contact hole. CONSTITUTION:After forming an oxide film 5 on a semiconductor substrate 1, a PSG film 6 is deposited. First, the surface is flattened and then a contact hole 7 is made in an interlayer insulating film comprising the PSG film 6 and the oxide film 5. Second, an Si3N4 film 11 is deposited to prevent Na<+> from penetrating. Furthermore, the whole body is annealed to implant ion in the PSG film 6 again. Third, the Si3N4 film 11 at the bottom of contact hole 7 is removed leaving the Si3N4 on sidewall part only. Finally, an aluminium film 12 is deposited and patterned to complete the contact hole and a wiring layer.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a nonvolatile semiconductor memory and a method for manufacturing the same, and particularly relates to an EPROM (Erasable PR
OM) and EBPROM (Fflextrical E
It is used in devices such as rasable PROM). Other devices such as DRAM (
Dynamic RAM), 8RAM (8tati
It can also be used in cases where it is desired to eliminate the influence of mobile ions as much as possible in the case where the influence of mobile ions is to be eliminated as much as possible.

(Prior art) Generally, in non-volatile memory, Ntx is used in the device.
The presence of mobile ions such as + causes deterioration of charge retention characteristics and instability of the threshold voltage of the cell transistor. Especially recently, non-volatile memory has come to be used in various fields, and it is often used in relatively high temperature environments, so the amount of mobile ions in the device is suppressed to a very low level. There is a need. In the prior art, Na attached to the wafer during the wafer process is generally immobilized through a getter process. For example, after forming a post-oxidation film, if a PSG film is deposited on top of it and subjected to high-temperature treatment, the attached Na is incorporated into the PSG film and becomes immobilized. This PSG film also prevents Na+ from entering from the outside.

(Problems to be Solved by the Invention) However, in this method, invasion of mobile ions through the contact hole cannot be prevented. After the high-temperature gettering process, contact holes are opened, but as shown in Figure 6, N
There is a risk that a+ may invade.

In FIG. 6, 1 is a semiconductor substrate, 2 is a memory cell portion, 3 is a floating gate), 4 is a control gate, 5 is a post-oxidation film, 6 is a PSG film, and 7 is a contact hole. Therefore, the post-oxidized film 5 does not act as a barrier against Na, etc. at all. Post-processing after contact opening and gold 4 such as At
There is a risk of mobile ions entering during the wiring layer formation process.
Moreover, since there is no high-temperature process after that, mobile ions cannot be gettered.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a highly reliable semiconductor memory that prevents the invasion of mobile ions from contact holes, and a method for manufacturing the same.

[Structure of the Invention] (Means and Effects for Solving the Problems) The present invention provides a non-volatile semiconductor memory cell formed on a semiconductor substrate, a single insulation film covering the memory cell, and a non-volatile semiconductor memory cell formed on a semiconductor substrate. A contact hole provided in the contact hole, a metal wiring layer passing through the contact hole, and a layer provided between this layer and the inner wall of the contact hole that allows more positive mobile ions to pass through than the 5i02 film. 1 feature. Further, a step of forming a nonvolatile semiconductor memory cell on a semiconductor substrate, a step of forming a glabella insulating film covering the memory cell,
forming a contact hole in the interlayer insulating film;
forming a layer on the inner wall of the contact hole that is more difficult for positive mobile ions to pass through than the Sio□ film; forming a metal wiring layer that passes through the contact hole; and after forming the layer that is more difficult for mobile ions to pass through; The second feature is that the method includes a step of increasing the temperature to 700° C. or higher before forming the metal wiring layer. That is, in the present invention, in order to prevent the invasion of mobile ions (mobile ions that are more positive than the StO□ film) from the contact hole, the side wall of the contact hole (
This method forms a film on the inner wall that makes it difficult for mobile ions to pass through, and prevents mobile ions that enter after the contact hole is opened, especially during the formation of the metal wiring layer. In addition, after forming a membrane that does not allow mobile ions to pass through,
If the process is carried out at a high temperature of 00°C or higher, the mobile ions that have entered the contact hole can be gettered into the interlayer insulation (e.g., PSG film) until a film is formed that is difficult for mobile ions to pass through, which further improves the effect. growing. Examples of the membrane that absorbs the mobile ions include St and N4 membranes.

(Example) An example of the present invention will be described below with reference to the drawings. 1st
Figures 5 through 5 are process diagrams of the same embodiment, but since they correspond to the case in Figure 6, corresponding parts will be given the same reference numerals and explanations will be omitted, and the description of the characteristic points will be omitted. Let's do it. First, after forming the post-oxide film 5 at 600X, the P8G film 6 is formed at approximately 600X.
01 is deposited (Fig. 1). Next, high-temperature heat treatment is performed for planarization, and at this time, mobile ions such as Na that have been introduced during the device process are gettered into the PSG film 6 (FIG. 2). Next, a contact hole 2 is opened in the interlayer insulating film composed of the PSG film 6 and the post-oxidized film 5 by photolithography (3rd-). Next, in order to prevent the invasion of KNa+, the Si, N4 film was heated at 500X, for example.
accumulate. % if re-diffusion to contacts is necessary.
It is preferable to perform ion implantation before depositing the 5s5N4 film.

Furthermore, annealing at 900° C. for 30 minutes is added to this. In this step, the 8 i 3N4 film 11 is removed from after the contact opening.
The mobile ions that have penetrated up to the time of deposition are taken into the P8G film 6 again (FIG. 4).

Next, 几IE (几aactlne Jon Etchin
By g), the S t 5N4 film 11 is left only in the contact hole. Next, an aluminum film 12 is deposited and patterned to complete the contact hole and wiring layer (FIG. 5).

According to the above embodiment, after opening the contact hole, especially A
5t of mobile ions that invade during the formation of t1lJ12.
You can play professionally with 3N4[7J. After forming the 5N4 film 1), once it passes through a high temperature process of 700℃ or more,
After the contact is opened, S t 5N invades and generates nine mobile ions into the PSG film 6 until the film 1 is formed.

It can be used for a variety of purposes, and the effect is even more intense.

[Effects of the Invention] As explained above, according to the present invention, in the nonvolatile memory produced using the present invention, the amount of mobile ions in the wafer is smaller than that of the conventional technology, and the reliability is improved. This results in a high quality device.

[Brief explanation of the drawing]

1 to 5 are process diagrams for explaining one embodiment of the present invention, and FIG. 6 is a sectional view of a conventional nonvolatile memory. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Memory cell part, 5...
Post-oxidation film, 6... PSG film, 7... Contact hole, 1)... S s 5N4 film, 12... At wiring. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (2)

[Claims] (1) A nonvolatile semiconductor memory cell formed on a semiconductor substrate, an interlayer insulating film covering this memory cell, a contact hole provided in this insulating film, a metal wiring layer passing through this contact hole, and this layer. A nonvolatile semiconductor memory characterized by comprising a layer provided between the inner wall of the contact hole and a layer through which positive mobile ions are more difficult to pass than the SiO_2 film. (2) forming a nonvolatile semiconductor memory cell on a semiconductor substrate; forming an interlayer insulating film covering the memory cell; forming a contact hole in the interlayer insulating film; A step of forming a layer through which positive mobile ions are more difficult to pass than the SiO_2 film, a step of forming a metal wiring layer passing through the contact hole, and a step after forming the layer through which mobile ions are more difficult to pass, but before forming the metal wiring layer. 1. A method for manufacturing a nonvolatile semiconductor memory, comprising the steps of: heating the memory to a high temperature of 700° C. or higher.