CN102064130A

CN102064130A - Method for forming SDMOS contact hole shape beneficial for filling metal

Info

Publication number: CN102064130A
Application number: CN2009102017881A
Authority: CN
Inventors: 房宝青; 张朝阳; 李江华; 孙效中
Original assignee: Shanghai Hua Hong NEC Electronics Co Ltd
Current assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Priority date: 2009-11-12
Filing date: 2009-11-12
Publication date: 2011-05-18
Anticipated expiration: 2029-11-12
Also published as: CN102064130B

Abstract

The invention discloses a method for forming a Schottky diode metal-oxide semiconductor (SDMOS) contact hole shape beneficial for filling a metal. The method comprises the following steps of: firstly, performing dry etching on a metal interlayer oxide after exposing a contact hole; secondly, performing primary contact hole etching and forming ohmic contact for subsequent connection between the contact hole and the metal; thirdly, performing primary contact hole ion injection; fourthly, performing secondary contact hole etching for forming an inverted trapezoidal structure with slight steps; fifthly, performing wet etching and back etching for etching a protruding interface of the metal interlayer oxide back and slightly retracting behind the interface of silicon; sixthly, chamfering by dry etching and planishing all steps; and finally, performing secondary contact hole ion injection, forming Schottky contact on the ion injection at the bottom of the contact hole, and forming the shape, beneficial for filling the metal, of the round-cornered and inverted-trapezoidal contact hole with a smooth sidewall. By using the method, a metal filling effect is good so as to improve the reliability of a device.

Description

Be beneficial to the formation method of metal filled SDMOS contact hole shape

Technical field

The invention belongs to semiconductor integrated circuit and make the field, relate in particular to a kind of formation method that is beneficial to metal filled SDMOS contact hole shape.

Background technology

The Schottky diode structure of SDMOS (integrated schottky power MOS transistor) is made in the contact hole bottom, then needs to inject respectively in source region formation ohmic contact with in contact hole bottom formation Schottky contacts with different ions.Concrete grammar comprises the steps (as shown in Figure 1): (1) is at the expose wet etching of laggard row metal interlevel oxidation thing 1 of contact hole; (2) carry out the dry etching of metal interlevel oxide 1; (3) first road contact hole etchings; (4) the contact hole ion injects 4 for the first time; (5) second road contact hole etchings; (6) the contact hole ion injects 5 for the second time; (7) metal 6 is filled.Carry out ion and be injected to the ohmic contact that is connected to form follow-up and metal behind the first road contact hole etching, carry out the second road etching then, the ion that carries out the contact hole bottom again injects and forms Schottky contacts.But the problem that occurs in this process is: in the process of the second road etching, the etch rate of injection region and non-injection region is different, can make that final contact hole sidewall is level and smooth inadequately, even up-narrow and down-wide situation appears, and obvious step is arranged between the different medium layer, cause metal to be difficult to complete filling in the hole, for follow-up reliability testing brings very big hidden danger.

As shown in Figure 2, some steps are arranged in this process, are respectively from top to bottom:

A. be with the wet etching of contact hole perforate expansion and the step of follow-up dry etching formation;

B. the step between metal interlevel oxide and the silicon;

C. the step that the silicon that has ion to inject and do not have ion to inject forms after etching.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of formation method that is beneficial to metal filled SDMOS contact hole shape, and this method makes metal filled respond well, thereby improves the reliability of device.

For solving the problems of the technologies described above, the invention provides a kind of formation method that is beneficial to metal filled SDMOS contact hole shape, form the contact hole of level and smooth inverted trapezoidal structure by following processing step:

Step 1. is at the expose dry etching of laggard row metal interlevel oxidation thing of contact hole;

Step 2. is contact hole etching for the first time, is the ohmic contact that is connected to form follow-up and metal;

Step 3. contact hole ion is for the first time injected;

Step 4. is contact hole etching for the second time, is formed with the inverted trapezoidal structure of slight step;

Step 5. wet etching returns quarter, the interface etching of outstanding metal interlevel oxide is gone back, and the back of slightly contracting is in the interface of silicon;

Step 6. dry etching chamfering polishes all steps;

Step 7. contact hole ion is for the second time injected, to the ion injection formation Schottky contacts of contact hole bottom.

In the step 2, described contact hole etching employing first time dry etching, the etch silicon degree of depth is 2000～4000 dusts.

In the step 4, described contact hole etching employing second time dry etching, this dry etching adopts gas CF4 and HBr, 0.04～0.1 liter/minute of flow, 60～100 watts of power, pressure 30～40 millitorrs, the etch silicon degree of depth is 2000～4000 dusts.

In the step 5, described wet etching returns to carve and is specially: the NH4HF2 of employing 3～10% and 30～40% NH4F mixture are as soup, and etch period is 3～5 minutes, and oxide thickness is 500～1000 dusts between etching sheet metal, make the contact hole opening bigger, form slight step.

In the step 6, described dry etching chamfering is specially: adopt gas O2 and CF4,0.02～0.1 liter/minute of flow, 60～100 watts of power, pressure 500～800 millitorrs, etch silicon 100～500 dusts all polish removal with step inside and outside the ion implanted region and above step.

Compare with prior art, the present invention has following beneficial effect: the present invention has overcome the difference of the etch rate that is caused by the ion injection, finally obtain fillet and fallen the smooth contact hole pattern of trapezoidal sidewall, made metal filled respond wellly, improved device reliability.

Description of drawings

Fig. 1 is the formation process chart of existing SDMOS contact hole; Wherein, the 1st, the metal interlevel oxide; The 2nd, the channel shaped grid; The 3rd, silicon substrate; The 4th, contact hole injects for the first time; The 5th, contact hole injects for the second time; The 6th, metal.

Fig. 2 is the schematic diagram of the contact hole with some steps of existing processes formation; Wherein, a. is with the wet etching of contact hole perforate expansion and the step of follow-up dry etching formation; B. the step between metal interlevel oxide and the silicon; C. the step that the silicon that has ion to inject and do not have ion to inject forms after etching.

Fig. 3 is a process chart of the present invention; Wherein, the 1st, the metal interlevel oxide; The 2nd, the channel shaped grid; The 3rd, silicon substrate; The 4th, contact hole injects for the first time; The 5th, contact hole injects for the second time; The 6th, metal.

Embodiment

The present invention is further detailed explanation below in conjunction with drawings and Examples.

Power MOS transistor is at contact hole bottom integrated schottky diode, and the influence that injected by the sidewall ion obtains up-small and down-big structure, and between the different medium layer obvious step arranged when the etching contact hole, be unfavorable for metal filled.Metal filled respond well in order to make, need the opening diameter of contact hole bigger, and the sidewall of contact hole is smooth more than base diameter, be beneficial to flowing of metal more, the contact hole that promptly obtains the smooth inverted trapezoidal structure of sidewall can improve metal filled effect.So the appearance step that the present invention is directed to three steps shown in Fig. 2 is improved:

1. in the existing processes flow process, after the contact hole exposure, the advanced hand-manipulating of needle is to the wet etching of metal interlevel oxide, and purpose is to allow the opening diameter of contact hole become big, be beneficial to the filling of follow-up metal, but the interface between wet etching and the dry etching has afterwards formed first step.

For removing this step, the present invention moves on to the back with wet etching, guaranteed that promptly contact hole has enough big diameter, can improve existing method again and produce up-small and down-big contact hole structure, and the metal interlevel oxide adopts the method for an etching (dry etching), has avoided the generation (dry etching of step 1. metal interlevel oxide) of first step.

2. the generation of the step between metal interlevel oxide and the silicon is because the metal interlevel oxide does not almost have loss in the etching process of follow-up contact hole silicon, and the silicon etch rate that is injected into is fast, and produces following diameter than top big pattern.This pattern can become the dead angle of follow-up metallic bond coat sputter, in metal filled process＞and surface tension that the turnings of 270 degree produce also will cause metal to be difficult to flow to the contact hole bottom.

For removing this turning, the present invention is after the contact hole silicon etching is finished, add a step wet etching, this wet etching can go back the interface etching of outstanding metal interlevel oxide, and the back of slightly contracting is in the interface of silicon, in the process of follow-up dry etching chamfering, this step also can be removed (step 5. wet etching returns and carves and step 6. dry etching chamfering).

3. the generation of the boundary of contact hole ion injection for the first time and non-injection zone comes from the difference of the etch rate of the silicon that is injected into and is not injected into, and this difference can be more obvious when the contact hole angle of sides is not enough.

The pattern of the contact hole etching difference of the etch rate that will alleviate the silicon that is injected into and is not injected into that tilts more for the second time; therefore the present invention has selected to contain the dry etching formula (gas CF4 and HBr) of protium; protium wherein will help to produce the polymer with sidewall protective effect; can obtain the bigger contact hole pattern of gradient, and the step that exists in this pattern can in follow-up dry etching chamfering step, be improved (step 4. for the second time contact hole etching and step 6. dry etching chamfering).

The method of thickness that in addition, can be by increasing the metal interlevel oxide guarantee residual metallic interlevel oxidation thing thickness and with the distance of grid.

As shown in Figure 3, the concrete steps of the inventive method are as follows:

Step 1. is etched to metal interlevel oxide 1 and silicon substrate 3 at the interface at the expose dry etching of laggard row metal interlevel oxidation thing 1 of contact hole;

Step 2. is contact hole etching for the first time, adopts dry etching, and dry etching adopts the process conditions of this area routine, and the degree of depth of etch silicon substrate 3 is 2000～4000 dusts;

Step 3. contact hole ion for the first time injects 4, is the ohmic contact that is connected to form follow-up and metal;

Step 4. is contact hole etching for the second time, adopts dry etching, adopts gas CF4 and HBr, 0.04～0.1 liter/minute of flow, 60～100 watts of power, pressure 30～40 millitorrs, be formed with the inverted trapezoidal structure of slight step, the degree of depth of etch silicon substrate 3 is 2000～4000 dusts;

Step 5. wet etching returns quarter, soup: NH4HF2 and NH4F, content: 3～10% NH4HF2,30～40% NH4F, etch period 3～5 minutes, the thickness of oxide 1 is 500～1000 dusts between etching sheet metal, the interface etching of outstanding metal interlevel oxide 1 is gone back, and slightly contract the back in the interface of silicon substrate 3, make the contact hole opening bigger, form slight step;

Step 6. dry etching chamfering adopts gas 02 and CF4,0.02～0.1 liter/minute of flow, 60～100 watts of power, pressure 500～800 millitorrs, about 100～500 dusts of the thickness of etch silicon substrate 3 all polish removal with step inside and outside the ion implanted region and above step;

Step 7. contact hole ion for the second time injects 5, to the ion injection formation Schottky contacts of contact hole bottom;

Step 8. metal 6 filling contact holes.

There is metal filled bad problem in existing SDMOS product, causes a hidden trouble for follow-up reliability.The present invention is by adjusting the formula of contact hole pattern and metal deposit, overcome by ion to inject and the etch rate difference that causes, falls the smooth contact hole pattern of trapezoidal sidewall thereby obtained fillet, finally obtained preferred metal and filled the result, sees Table 1.

Table 1

Claims

1. a formation method that is beneficial to metal filled SDMOS contact hole shape is characterized in that, forms the contact hole of level and smooth inverted trapezoidal structure by following processing step:

Step 3. contact hole ion is for the first time injected;

Step 6. dry etching chamfering polishes all steps;

2. the formation method that is beneficial to metal filled SDMOS contact hole shape as claimed in claim 1 is characterized in that, in the step 2, and described contact hole etching employing first time dry etching, the etch silicon degree of depth is 2000～4000 dusts.

3. the formation method that is beneficial to metal filled SDMOS contact hole shape as claimed in claim 1, it is characterized in that, in the step 4, described contact hole etching employing second time dry etching, this dry etching adopts gas CF4 and HBr, 0.04～0.1 liter/minute of flow, 60～100 watts of power, pressure 30～40 millitorrs, the etch silicon degree of depth are 2000～4000 dusts.

4. the formation method that is beneficial to metal filled SDMOS contact hole shape as claimed in claim 1, it is characterized in that, in the step 5, described wet etching returns to carve and is specially: the NH4HF2 of employing 3～10% and 30～40% NH4F mixture are as soup, etch period is 3～5 minutes, oxide thickness is 500～1000 dusts between etching sheet metal, makes the contact hole opening bigger, forms slight step.

5. the formation method that is beneficial to metal filled SDMOS contact hole shape as claimed in claim 1, it is characterized in that, in the step 6, described dry etching chamfering is specially: adopt gas O2 and CF4,0.02～0.1 liter/minute of flow, 60～100 watts of power, pressure 500～800 millitorrs, etch silicon 100～500 dusts all polish removal with step inside and outside the ion implanted region and above step.